tracing/tracing/metrics/system_health/memory_metric.html

<!DOCTYPE html>
<!--
Copyright 2016 The Chromium Authors. All rights reserved.
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<link rel="import" href="/tracing/base/math/range.html">
<link rel="import" href="/tracing/base/multi_dimensional_view.html">
<link rel="import" href="/tracing/base/unit.html">
<link rel="import" href="/tracing/base/utils.html">
<link rel="import" href="/tracing/extras/chrome/chrome_processes.html">
<link rel="import" href="/tracing/metrics/metric_registry.html">
<link rel="import" href="/tracing/metrics/system_health/utils.html">
<link rel="import" href="/tracing/model/container_memory_dump.html">
<link rel="import" href="/tracing/model/helpers/chrome_model_helper.html">
<link rel="import" href="/tracing/model/memory_allocator_dump.html">
<link rel="import" href="/tracing/value/diagnostics/breakdown.html">
<link rel="import" href="/tracing/value/histogram.html">

<script>
'use strict';

tr.exportTo('tr.metrics.sh', function() {
  const BACKGROUND = tr.model.ContainerMemoryDump.LevelOfDetail.BACKGROUND;
  const LIGHT = tr.model.ContainerMemoryDump.LevelOfDetail.LIGHT;
  const DETAILED = tr.model.ContainerMemoryDump.LevelOfDetail.DETAILED;
  const sizeInBytes_smallerIsBetter =
      tr.b.Unit.byName.sizeInBytes_smallerIsBetter;
  const count_smallerIsBetter = tr.b.Unit.byName.count_smallerIsBetter;
  const DISPLAYED_SIZE_NUMERIC_NAME =
      tr.model.MemoryAllocatorDump.DISPLAYED_SIZE_NUMERIC_NAME;

  const LEVEL_OF_DETAIL_NAMES = new Map();
  LEVEL_OF_DETAIL_NAMES.set(BACKGROUND, 'background');
  LEVEL_OF_DETAIL_NAMES.set(LIGHT, 'light');
  LEVEL_OF_DETAIL_NAMES.set(DETAILED, 'detailed');

  // Some detailed dumps contain heap profiler information.
  const HEAP_PROFILER_DETAIL_NAME = 'heap_profiler';

  const BOUNDARIES_FOR_UNIT_MAP = new WeakMap();
  // For unitless numerics (process counts), we use 20 linearly scaled bins
  // from 0 to 20.
  BOUNDARIES_FOR_UNIT_MAP.set(count_smallerIsBetter,
      tr.v.HistogramBinBoundaries.createLinear(0, 20, 20));
  // For size numerics (subsystem and vm stats), we use 1 bin from 0 B to
  // 1 KiB and 4*24 exponentially scaled bins from 1 KiB to 16 GiB (=2^24 KiB).
  BOUNDARIES_FOR_UNIT_MAP.set(sizeInBytes_smallerIsBetter,
      new tr.v.HistogramBinBoundaries(0)
          .addBinBoundary(1024 /* 1 KiB */)
          .addExponentialBins(16 * 1024 * 1024 * 1024 /* 16 GiB */, 4 * 24));

  const CHROME_PROCESS_NAMES =
      tr.e.chrome.chrome_processes.CHROME_PROCESS_NAMES;

  function memoryMetric(values, model, opt_options) {
    const rangeOfInterest =
      opt_options ? opt_options.rangeOfInterest : undefined;
    const browserNameToGlobalDumps =
        tr.metrics.sh.splitGlobalDumpsByBrowserName(model, rangeOfInterest);
    addGeneralMemoryDumpValues(browserNameToGlobalDumps, values);
    addDetailedMemoryDumpValues(browserNameToGlobalDumps, values);
    addMemoryDumpCountValues(browserNameToGlobalDumps, values);
  }

  const USER_FRIENDLY_BROWSER_NAMES = {
    'chrome': 'Chrome',
    'webview': 'WebView',
    'unknown_browser': 'an unknown browser'
  };

  /**
   * Convert a canonical browser name used in value names to a user-friendly
   * name used in value descriptions.
   *
   * Examples:
   *
   *   CANONICAL BROWSER NAME -> USER-FRIENDLY NAME
   *   chrome                 -> Chrome
   *   unknown_browser        -> an unknown browser
   *   webview2               -> WebView(2)
   *   unexpected             -> 'unexpected' browser
   */
  function convertBrowserNameToUserFriendlyName(browserName) {
    for (const baseName in USER_FRIENDLY_BROWSER_NAMES) {
      if (!browserName.startsWith(baseName)) continue;

      const userFriendlyBaseName = USER_FRIENDLY_BROWSER_NAMES[baseName];
      const suffix = browserName.substring(baseName.length);
      if (suffix.length === 0) {
        return userFriendlyBaseName;
      } else if (/^\d+$/.test(suffix)) {
        return userFriendlyBaseName + '(' + suffix + ')';
      }
    }
    return '\'' + browserName + '\' browser';
  }


  /**
   * Convert a canonical process name used in value names to a user-friendly
   * name used in value descriptions.
   */
  function convertProcessNameToUserFriendlyName(processName,
      opt_requirePlural) {
    switch (processName) {
      case CHROME_PROCESS_NAMES.BROWSER:
        return opt_requirePlural ? 'browser processes' : 'the browser process';
      case CHROME_PROCESS_NAMES.RENDERER:
        return 'renderer processes';
      case CHROME_PROCESS_NAMES.GPU:
        return opt_requirePlural ? 'GPU processes' : 'the GPU process';
      case CHROME_PROCESS_NAMES.PPAPI:
        return opt_requirePlural ? 'PPAPI processes' : 'the PPAPI process';
      case CHROME_PROCESS_NAMES.ALL:
        return 'all processes';
      case CHROME_PROCESS_NAMES.UNKNOWN:
        return 'unknown processes';
      default:
        return '\'' + processName + '\' processes';
    }
  }

  /**
   * Add general memory dump values calculated from all global memory dumps to
   * |values|. In particular, this function adds the following values:
   *
   *   * PROCESS COUNTS
   *     memory:{chrome, webview}:
   *         {browser_process, renderer_processes, ..., all_processes}:
   *         process_count
   *     type: tr.v.Histogram (over all matching global memory dumps)
   *     unit: count_smallerIsBetter
   *
   *   * MEMORY USAGE REPORTED BY CHROME
   *     memory:{chrome, webview}:
   *         {browser_process, renderer_processes, ..., all_processes}:
   *         reported_by_chrome[:{v8, malloc, ...}]:
   *         {effective_size, allocated_objects_size, locked_size}
   *     type: tr.v.Histogram (over all matching global memory dumps)
   *     unit: sizeInBytes_smallerIsBetter
   */
  function addGeneralMemoryDumpValues(browserNameToGlobalDumps, values) {
    addMemoryDumpValues(browserNameToGlobalDumps,
        gmd => true /* process all global memory dumps */,
        function(processDump, addProcessScalar) {
          // Increment memory:<browser-name>:<process-name>:process_count value.
          addProcessScalar({
            source: 'process_count',
            property: PROCESS_COUNT,
            value: 1
          });

          if (processDump.totals !== undefined) {
            addProcessScalar({
              source: 'reported_by_os',
              property: RESIDENT_SIZE,
              component: ['system_memory'],
              value: processDump.totals.residentBytes
            });
            addProcessScalar({
              source: 'reported_by_os',
              property: PEAK_RESIDENT_SIZE,
              component: ['system_memory'],
              value: processDump.totals.peakResidentBytes
            });
            addProcessScalar({
              source: 'reported_by_os',
              property: PRIVATE_FOOTPRINT_SIZE,
              component: ['system_memory'],
              value: processDump.totals.privateFootprintBytes,
            });
          }

          // Add memory:<browser-name>:<process-name>:reported_by_chrome:...
          // values.
          if (processDump.memoryAllocatorDumps === undefined) return;

          processDump.memoryAllocatorDumps.forEach(function(rootAllocatorDump) {
            CHROME_VALUE_PROPERTIES.forEach(function(property) {
              addProcessScalar({
                source: 'reported_by_chrome',
                component: [rootAllocatorDump.name],
                property,
                value: rootAllocatorDump.numerics[property.name]
              });
            });
            // Some dump providers add allocated objects size as
            // "allocated_objects" child dump.
            if (rootAllocatorDump.numerics.allocated_objects_size ===
                    undefined) {
              const allocatedObjectsDump =
                  rootAllocatorDump.getDescendantDumpByFullName(
                      'allocated_objects');
              if (allocatedObjectsDump !== undefined) {
                addProcessScalar({
                  source: 'reported_by_chrome',
                  component: [rootAllocatorDump.name],
                  property: ALLOCATED_OBJECTS_SIZE,
                  value: allocatedObjectsDump.numerics.size
                });
              }
            }
          });

          // Add memory:<browser-name>:<process-name>:reported_by_chrome:
          //    {malloc, blinkgc, partitionalloc}:<largestCategory>:...
          addTopHeapDumpCategoryValue(processDump, addProcessScalar);

          // Add memory:<browser-name>:<process-name>:reported_by_chrome:v8:
          //     {heap, allocated_by_malloc}:...
          addV8MemoryDumpValues(processDump, addProcessScalar);
        },
        function(componentTree) {
          // Subtract memory:<browser-name>:<process-name>:reported_by_chrome:
          // tracing:<size-property> from memory:<browser-name>:<process-name>:
          // reported_by_chrome:<size-property> if applicable.
          const tracingNode = componentTree.children[1].get('tracing');
          if (tracingNode === undefined) return;

          for (let i = 0; i < componentTree.values.length; i++) {
            componentTree.values[i].total -= tracingNode.values[i].total;
          }
        }, values);
  }

  /**
   * Add memory dump values for the top category in each allocator heap dump in
   * the process dump.
   *
   * @param {!tr.model.ProcessMemoryDump} processDump The process memory dump.
   * @param {!function} addProcessScalar The callback for adding a scalar value.
   */
  function addTopHeapDumpCategoryValue(processDump, addProcessScalar) {
    if (!processDump.heapDumps) {
      return;
    }
    for (const allocatorName in processDump.heapDumps) {
      const heapDump = processDump.heapDumps[allocatorName];
      if (heapDump.entries === undefined || heapDump.entries.length === 0) {
        return;
      }
      // Create a map of category to total size.
      const typeToSize = {};
      for (let i = 0; i < heapDump.entries.length; i += 1) {
        const entry = heapDump.entries[i];
        // Count only the entries with empty backtrace which contains totals for
        // the object type.
        if (!entry.objectTypeName || entry.leafStackFrame) {
          continue;
        }
        if (!typeToSize[entry.objectTypeName]) {
          typeToSize[entry.objectTypeName] = 0;
        }
        typeToSize[entry.objectTypeName] += entry.size;
      }

      // Find the largest type in the heap dump.
      let largestValue = 0;
      let largestType = '';
      for (const key in typeToSize) {
        if (largestValue < typeToSize[key]) {
          largestValue = typeToSize[key];
          largestType = key;
        }
      }
      addProcessScalar({
        source: 'reported_by_chrome',
        component: [allocatorName, largestType],
        property: HEAP_CATEGORY_SIZE,
        value: largestValue
      });
    }
  }

  /**
   * Add memory dump values calculated from V8 components excluding
   * 'heap_spaces/other_spaces'.
   *
   * @param {!tr.model.ProcessMemoryDump} processDump The process memory dump.
   * @param {!function} addProcessScalar The callback for adding a scalar value.
   */
  function addV8MemoryDumpValues(processDump, addProcessScalar) {
    const v8Dump = processDump.getMemoryAllocatorDumpByFullName('v8');
    if (v8Dump === undefined) return;

    const sharedDump = v8Dump.getDescendantDumpByFullName('shared');
    if (sharedDump !== undefined) {
      addV8ComponentValues(sharedDump, ['v8', 'shared'],
          addProcessScalar);
      sharedDump.children.forEach(function(subDump) {
        addV8ComponentValues(subDump, ['v8', 'shared', subDump.name],
            addProcessScalar);
      });
    }

    v8Dump.children.forEach(function(isolateDump) {
      // v8:allocated_by_malloc:...
      const mallocDump = isolateDump.getDescendantDumpByFullName('malloc');
      if (mallocDump !== undefined) {
        addV8ComponentValues(mallocDump, ['v8', 'allocated_by_malloc'],
            addProcessScalar);
      }
      // v8:heap:...
      let heapDump = isolateDump.getDescendantDumpByFullName('heap');
      if (heapDump === undefined) {
        // Old V8 memory dumps call this 'heap_spaces'.
        heapDump = isolateDump.getDescendantDumpByFullName('heap_spaces');
      }
      if (heapDump !== undefined) {
        addV8ComponentValues(heapDump, ['v8', 'heap'], addProcessScalar);
        heapDump.children.forEach(function(spaceDump) {
          if (spaceDump.name === 'other_spaces') return;

          addV8ComponentValues(spaceDump, ['v8', 'heap', spaceDump.name],
              addProcessScalar);
        });
      }
    });

    // V8 generates bytecode when interpreting and code objects when
    // compiling the javascript. Total code size includes the size
    // of code and bytecode objects.
    addProcessScalar({
      source: 'reported_by_chrome',
      component: ['v8'],
      property: CODE_AND_METADATA_SIZE,
      value: v8Dump.numerics.code_and_metadata_size
    });
    addProcessScalar({
      source: 'reported_by_chrome',
      component: ['v8'],
      property: CODE_AND_METADATA_SIZE,
      value: v8Dump.numerics.bytecode_and_metadata_size
    });
  }

  /**
   * Add memory dump values calculated from the specified V8 component.
   *
   * @param {!tr.model.MemoryAllocatorDump} v8Dump The V8 memory dump.
   * @param {!Array<string>} componentPath The component path for reporting.
   * @param {!function} addProcessScalar The callback for adding a scalar value.
   */
  function addV8ComponentValues(componentDump, componentPath,
      addProcessScalar) {
    CHROME_VALUE_PROPERTIES.forEach(function(property) {
      addProcessScalar({
        source: 'reported_by_chrome',
        component: componentPath,
        property,
        value: componentDump.numerics[property.name]
      });
    });
  }

  const PROCESS_COUNT = {
    unit: count_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      if (componentPath.length > 0) {
        throw new Error('Unexpected process count non-empty component path: ' +
            componentPath.join(':'));
      }
      return 'total number of ' + convertProcessNameToUserFriendlyName(
          processName, true /* opt_requirePlural */);
    }
  };

  const EFFECTIVE_SIZE = {
    name: 'effective_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'effective size',
        componentPreposition: 'of'
      });
    }
  };

  const ALLOCATED_OBJECTS_SIZE = {
    name: 'allocated_objects_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'size of all objects allocated',
        totalUserFriendlyPropertyName: 'size of all allocated objects',
        componentPreposition: 'by'
      });
    }
  };

  const MAX_ALLOCATED_SIZE = {
    name: 'max_allocated_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'max size of all allocations',
        componentPreposition: 'of'
      });
    }
  };

  const MAX_COMMITTED_SIZE = {
    name: 'max_committed_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'max size of all committed memory',
        componentPreposition: 'of'
      });
    }
  };

  const SHIM_ALLOCATED_OBJECTS_SIZE = {
    name: 'shim_allocated_objects_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'size of all objects allocated through shim',
        totalUserFriendlyPropertyName:
            'size of all allocated objects through shim',
        componentPreposition: 'by'
      });
    }
  };

  const LOCKED_SIZE = {
    name: 'locked_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'locked (pinned) size',
        componentPreposition: 'of'
      });
    }
  };

  const PEAK_SIZE = {
    name: 'peak_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'peak size',
        componentPreposition: 'of'
      });
    }
  };

  const HEAP_CATEGORY_SIZE = {
    name: 'heap_category_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyName: 'heap profiler category size',
        componentPreposition: 'for'
      });
    }
  };

  const CODE_AND_METADATA_SIZE = {
    name: 'code_and_metadata_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildChromeValueDescriptionPrefix(componentPath, processName, {
        userFriendlyPropertyNamePrefix: 'size of',
        userFriendlyPropertyName: 'code and metadata'
      });
    }
  };

  const CHROME_VALUE_PROPERTIES = [
    EFFECTIVE_SIZE,
    ALLOCATED_OBJECTS_SIZE,
    SHIM_ALLOCATED_OBJECTS_SIZE,
    MAX_ALLOCATED_SIZE,
    MAX_COMMITTED_SIZE,
    LOCKED_SIZE,
    PEAK_SIZE
  ];

  /**
   * Build a description prefix for a memory:<browser-name>:<process-name>:
   * reported_by_chrome:... value.
   *
   * @param {!Array<string>} componentPath The underlying component path (e.g.
   *     ['malloc']).
   * @param {string} processName The canonical name of the process.
   * @param {{
   *     userFriendlyPropertyName: string,
   *     userFriendlyPropertyNamePrefix: (string|undefined),
   *     totalUserFriendlyPropertyName: (string|undefined),
   *     componentPreposition: (string|undefined) }}
   *     formatSpec Specification of how the property should be formatted.
   * @return {string} Prefix for the value's description (e.g.
   *     'effective size of malloc in the browser process').
   */
  function buildChromeValueDescriptionPrefix(
      componentPath, processName, formatSpec) {
    const nameParts = [];
    if (componentPath.length === 0) {
      nameParts.push('total');
      if (formatSpec.totalUserFriendlyPropertyName) {
        nameParts.push(formatSpec.totalUserFriendlyPropertyName);
      } else {
        if (formatSpec.userFriendlyPropertyNamePrefix) {
          nameParts.push(formatSpec.userFriendlyPropertyNamePrefix);
        }
        nameParts.push(formatSpec.userFriendlyPropertyName);
      }
      nameParts.push('reported by Chrome for');
    } else {
      if (formatSpec.componentPreposition === undefined) {
        // Use component name as an adjective
        // (e.g. 'size of V8 code and metadata').
        if (formatSpec.userFriendlyPropertyNamePrefix) {
          nameParts.push(formatSpec.userFriendlyPropertyNamePrefix);
        }
        nameParts.push(componentPath.join(':'));
        nameParts.push(formatSpec.userFriendlyPropertyName);
      } else {
        // Use component name as a noun with a preposition
        // (e.g. 'size of all objects allocated BY MALLOC').
        if (formatSpec.userFriendlyPropertyNamePrefix) {
          nameParts.push(formatSpec.userFriendlyPropertyNamePrefix);
        }
        nameParts.push(formatSpec.userFriendlyPropertyName);
        nameParts.push(formatSpec.componentPreposition);
        if (componentPath[componentPath.length - 1] === 'allocated_by_malloc') {
          nameParts.push('objects allocated by malloc for');
          nameParts.push(
              componentPath.slice(0, componentPath.length - 1).join(':'));
        } else {
          nameParts.push(componentPath.join(':'));
        }
      }
      nameParts.push('in');
    }
    nameParts.push(convertProcessNameToUserFriendlyName(processName));
    return nameParts.join(' ');
  }

  const RESIDENT_SIZE = {
    name: 'resident_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'resident set size (RSS)');
    }
  };

  const PEAK_RESIDENT_SIZE = {
    name: 'peak_resident_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'peak resident set size');
    }
  };

  const PROPORTIONAL_RESIDENT_SIZE = {
    name: 'proportional_resident_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'proportional resident size (PSS)');
    }
  };

  const PRIVATE_DIRTY_SIZE = {
    name: 'private_dirty_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'private dirty size');
    }
  };

  const PRIVATE_FOOTPRINT_SIZE = {
    name: 'private_footprint_size',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'private footprint size');
    }
  };

  const JAVA_BASE_CLEAN_RESIDENT = {
    name: 'java_base_clean_resident',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'java base odex and vdex total clean resident size');
    }
  };

  const JAVA_BASE_PSS = {
    name: 'java_base_pss',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'java base odex and vdex proportional resident size');
    }
  };

  const NATIVE_LIBRARY_PRIVATE_CLEAN_RESIDENT = {
    name: 'native_library_private_clean_resident',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'native library private clean resident size');
    }
  };

  const NATIVE_LIBRARY_SHARED_CLEAN_RESIDENT = {
    name: 'native_library_shared_clean_resident',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'native library shared clean resident size');
    }
  };

  const NATIVE_LIBRARY_PROPORTIONAL_RESIDENT = {
    name: 'native_library_proportional_resident',
    unit: sizeInBytes_smallerIsBetter,
    buildDescriptionPrefix(componentPath, processName) {
      return buildOsValueDescriptionPrefix(componentPath, processName,
          'native library proportional resident size');
    }
  };

  /**
   * Build a description prefix for a memory:<browser-name>:<process-name>:
   * reported_by_os:... value.
   *
   * @param {!Array<string>} componentPath The underlying component path (e.g.
   *     ['system', 'java_heap']).
   * @param {string} processName The canonical name of the process.
   * @param {string} userFriendlyPropertyName User-friendly name of the
   *     underlying property (e.g. 'private dirty size').
   * @return {string} Prefix for the value's description (e.g.
   *     'total private dirty size of the Java heal in the GPU process').
   */
  function buildOsValueDescriptionPrefix(
      componentPath, processName, userFriendlyPropertyName) {
    if (componentPath.length > 2) {
      throw new Error('OS value component path for \'' +
          userFriendlyPropertyName + '\' too long: ' + componentPath.join(':'));
    }

    const nameParts = [];
    if (componentPath.length < 2) {
      nameParts.push('total');
    }

    nameParts.push(userFriendlyPropertyName);

    if (componentPath.length > 0) {
      switch (componentPath[0]) {
        case 'system_memory':
          if (componentPath.length > 1) {
            const userFriendlyComponentName =
                SYSTEM_VALUE_COMPONENTS[componentPath[1]].userFriendlyName;
            if (userFriendlyComponentName === undefined) {
              throw new Error('System value sub-component for \'' +
                  userFriendlyPropertyName + '\' unknown: ' +
                  componentPath.join(':'));
            }
            nameParts.push('of', userFriendlyComponentName, 'in');
          } else {
            nameParts.push('of system memory (RAM) used by');
          }
          break;

        case 'gpu_memory':
          if (componentPath.length > 1) {
            nameParts.push('of the', componentPath[1]);
            nameParts.push('Android memtrack component in');
          } else {
            nameParts.push('of GPU memory (Android memtrack) used by');
          }
          break;

        default:
          throw new Error('OS value component for \'' +
              userFriendlyPropertyName + '\' unknown: ' +
              componentPath.join(':'));
      }
    } else {
      nameParts.push('reported by the OS for');
    }

    nameParts.push(convertProcessNameToUserFriendlyName(processName));
    return nameParts.join(' ');
  }

  /**
   * Add heavy memory dump values calculated from heavy global memory dumps to
   * |values|. In particular, this function adds the following values:
   *
   *   * MEMORY USAGE REPORTED BY THE OS
   *     memory:{chrome, webview}:
   *         {browser_process, renderer_processes, ..., all_processes}:
   *         reported_by_os:system_memory:[{ashmem, native_heap, java_heap}:]
   *         {proportional_resident_size, private_dirty_size}
   *     memory:{chrome, webview}:
   *         {browser_process, renderer_processes, ..., all_processes}:
   *         reported_by_os:gpu_memory:[{gl, graphics, ...}:]
   *         proportional_resident_size
   *     type: tr.v.Histogram (over matching heavy global memory dumps)
   *     unit: sizeInBytes_smallerIsBetter
   *
   *   * MEMORY USAGE REPORTED BY CHROME
   *     memory:{chrome, webview}:
   *         {browser_process, renderer_processes, ..., all_processes}:
   *         reported_by_chrome:v8:code_and_metadata_size
   *     type: tr.v.Histogram (over matching heavy global memory dumps)
   *     unit: sizeInBytes_smallerIsBetter
   */
  function addDetailedMemoryDumpValues(browserNameToGlobalDumps, values) {
    addMemoryDumpValues(browserNameToGlobalDumps,
        g => g.levelOfDetail === DETAILED,
        function(processDump, addProcessScalar) {
          // Add memory:<browser-name>:<process-name>:reported_by_os:
          // system_memory:... values.
          for (const [componentName, componentSpec] of
            Object.entries(SYSTEM_VALUE_COMPONENTS)) {
            const node = getDescendantVmRegionClassificationNode(
                processDump.vmRegions, componentSpec.classificationPath);
            const componentPath = ['system_memory'];
            if (componentName) componentPath.push(componentName);
            addProcessScalar({
              source: 'reported_by_os',
              component: componentPath,
              property: PROPORTIONAL_RESIDENT_SIZE,
              value: node === undefined ?
                0 : (node.byteStats.proportionalResident || 0)
            });
            addProcessScalar({
              source: 'reported_by_os',
              component: componentPath,
              property: PRIVATE_DIRTY_SIZE,
              value: node === undefined ?
                0 : (node.byteStats.privateDirtyResident || 0)
            });

            // Only add java base stats when they are nonzero.
            if (node) {
              if (node.byteStats.javaBasePss) {
                addProcessScalar({
                  source: 'reported_by_os',
                  component: componentPath,
                  property: JAVA_BASE_PSS,
                  value: node.byteStats.javaBasePss
                });
              }
              if (node.byteStats.javaBaseCleanResident) {
                addProcessScalar({
                  source: 'reported_by_os',
                  component: componentPath,
                  property: JAVA_BASE_CLEAN_RESIDENT,
                  value: node.byteStats.javaBaseCleanResident
                });
              }
            }

            // Only add native library stats when they are nonzero.
            if (node) {
              if (node.byteStats.nativeLibraryPrivateCleanResident) {
                addProcessScalar({
                  source: 'reported_by_os',
                  component: componentPath,
                  property: NATIVE_LIBRARY_PRIVATE_CLEAN_RESIDENT,
                  value: node.byteStats.nativeLibraryPrivateCleanResident
                });
              }
              if (node.byteStats.nativeLibrarySharedCleanResident) {
                addProcessScalar({
                  source: 'reported_by_os',
                  component: componentPath,
                  property: NATIVE_LIBRARY_SHARED_CLEAN_RESIDENT,
                  value: node.byteStats.nativeLibrarySharedCleanResident
                });
              }
              if (node.byteStats.nativeLibraryProportionalResident) {
                addProcessScalar({
                  source: 'reported_by_os',
                  component: componentPath,
                  property: NATIVE_LIBRARY_PROPORTIONAL_RESIDENT,
                  value: node.byteStats.nativeLibraryProportionalResident
                });
              }
            }
          }

          // Add memory:<browser-name>:<process-name>:reported_by_os:
          // gpu_memory:... values.
          const memtrackDump = processDump.getMemoryAllocatorDumpByFullName(
              'gpu/android_memtrack');
          if (memtrackDump !== undefined) {
            memtrackDump.children.forEach(function(memtrackChildDump) {
              addProcessScalar({
                source: 'reported_by_os',
                component: ['gpu_memory', memtrackChildDump.name],
                property: PROPORTIONAL_RESIDENT_SIZE,
                value: memtrackChildDump.numerics.memtrack_pss
              });
            });
          }
        }, function(componentTree) {}, values);
  }

  // Specifications of components reported by the system.
  const SYSTEM_VALUE_COMPONENTS = {
    '': {
      classificationPath: [],
    },
    'java_heap': {
      classificationPath: ['Android', 'Java runtime', 'Spaces'],
      userFriendlyName: 'the Java heap'
    },
    'ashmem': {
      classificationPath: ['Android', 'Ashmem'],
      userFriendlyName: 'ashmem'
    },
    'native_heap': {
      classificationPath: ['Native heap'],
      userFriendlyName: 'the native heap'
    },
    'stack': {
      classificationPath: ['Stack'],
      userFriendlyName: 'the thread stacks'
    }
  };

  /**
   * Get the descendant of a VM region classification |node| specified by the
   * given |path| of child node titles. If |node| is undefined or such a
   * descendant does not exist, this function returns undefined.
   */
  function getDescendantVmRegionClassificationNode(node, path) {
    for (let i = 0; i < path.length; i++) {
      if (node === undefined) break;

      node = node.children.find(c => c.title === path[i]);
    }
    return node;
  }

  /**
   * Add global memory dump counts to |values|. In particular, this function
   * adds the following values:
   *
   *   * DUMP COUNTS
   *     memory:{chrome, webview}:all_processes:dump_count
   *         [:{light, detailed, heap_profiler}]
   *     type: tr.v.Histogram
   *     unit: count_smallerIsBetter
   *
   * Note that unlike all other values generated by the memory metric, the
   * global memory dump counts are NOT instances of tr.v.Histogram
   * because it doesn't make sense to aggregate them (they are already counts
   * over all global dumps associated with the relevant browser).
   */
  function addMemoryDumpCountValues(browserNameToGlobalDumps, values) {
    browserNameToGlobalDumps.forEach(function(globalDumps, browserName) {
      let totalDumpCount = 0;
      const levelOfDetailNameToDumpCount = {};
      LEVEL_OF_DETAIL_NAMES.forEach(function(levelOfDetailName) {
        levelOfDetailNameToDumpCount[levelOfDetailName] = 0;
      });
      levelOfDetailNameToDumpCount[HEAP_PROFILER_DETAIL_NAME] = 0;

      globalDumps.forEach(function(globalDump) {
        totalDumpCount++;

        // Increment the level-of-detail-specific dump count (if possible).
        const levelOfDetailName =
            LEVEL_OF_DETAIL_NAMES.get(globalDump.levelOfDetail);
        if (levelOfDetailName === undefined) {
          return;  // Unknown level of detail.
        }
        levelOfDetailNameToDumpCount[levelOfDetailName]++;
        if (globalDump.levelOfDetail === DETAILED) {
          if (detectHeapProfilerInMemoryDump(globalDump)) {
            levelOfDetailNameToDumpCount[HEAP_PROFILER_DETAIL_NAME]++;
          }
        }
      });

      // Add memory:<browser-name>:all_processes:dump_count[:<level>] values.
      reportMemoryDumpCountAsValue(browserName, undefined /* total */,
          totalDumpCount, values);
      for (const [levelOfDetailName, levelOfDetailDumpCount] of
        Object.entries(levelOfDetailNameToDumpCount)) {
        reportMemoryDumpCountAsValue(browserName, levelOfDetailName,
            levelOfDetailDumpCount, values);
      }
    });
  }

  /**
   * Check whether detailed global dump has heap profiler information or not.
   */
  function detectHeapProfilerInMemoryDump(globalDump) {
    for (const processDump of Object.values(globalDump.processMemoryDumps)) {
      if (processDump.heapDumps && processDump.heapDumps.malloc) {
        const mallocDump = processDump.heapDumps.malloc;
        if (mallocDump.entries && mallocDump.entries.length > 0) {
          return true;
        }
      }
    }
    return false;
  }

  /**
   * Add a tr.v.Histogram value to |values| reporting that the number of
   * |levelOfDetailName| memory dumps added by |browserName| was
   * |levelOfDetailCount|.
   */
  function reportMemoryDumpCountAsValue(
      browserName, levelOfDetailName, levelOfDetailDumpCount, values) {
    // Construct the name of the memory value.
    const nameParts = ['memory', browserName, 'all_processes', 'dump_count'];
    if (levelOfDetailName !== undefined) {
      nameParts.push(levelOfDetailName);
    }
    const name = nameParts.join(':');

    // Build the underlying histogram for the memory value.
    const histogram = new tr.v.Histogram(name, count_smallerIsBetter,
        BOUNDARIES_FOR_UNIT_MAP.get(count_smallerIsBetter));
    histogram.addSample(levelOfDetailDumpCount);

    // If |levelOfDetail| argument is undefined it means a total value.
    const userFriendlyLevelOfDetail =
        (levelOfDetailName || 'all').replace('_', ' ');

    // Build the options for the memory value.
    histogram.description = [
      'total number of',
      userFriendlyLevelOfDetail,
      'memory dumps added by',
      convertBrowserNameToUserFriendlyName(browserName),
      'to the trace'
    ].join(' ');

    // Report the memory value.
    values.addHistogram(histogram);
  }

  /**
   * Add generic values extracted from process memory dumps and aggregated by
   * process name and component path into |values|.
   *
   * For each browser and set of global dumps in |browserNameToGlobalDumps|,
   * |customProcessDumpValueExtractor| is applied to every process memory dump
   * associated with the global memory dump. The second argument provided to the
   * callback is a function for adding extracted values:
   *
   *   function sampleProcessDumpCallback(processDump, addProcessValue) {
   *     ...
   *     addProcessScalar({
   *       source: 'reported_by_chrome',
   *       component: ['system', 'native_heap'],
   *       property: 'proportional_resident_size',
   *       value: pssExtractedFromProcessDump2,
   *       descriptionPrefixBuilder(componentPath) {
   *         return 'PSS of ' + componentPath.join('/') + ' in';
   *       }
   *     });
   *     ...
   *   }
   *
   * For each global memory dump, the extracted values are summed by process
   * name (browser_process, renderer_processes, ..., all_processes) and
   * component path (e.g. gpu is a sum of gpu:gl, gpu:graphics, ...). The sums
   * are then aggregated over all global memory dumps associated with the given
   * browser. For example, assuming that |customProcessDumpValueExtractor|
   * extracts 'proportional_resident_size' values for component paths
   * ['X', 'A'], ['X', 'B'] and ['Y'] under the same 'source' from each process
   * memory dump, the following values will be reported (for Chrome):
   *
   *    memory:chrome:browser_process:source:X:A:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A in all 'browser' process dumps in global dump 1,
   *          ...
   *          sum of X:A in all 'browser' process dumps in global dump N
   *        ]
   *
   *    memory:chrome:browser_process:source:X:B:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:B in all 'browser' process dumps in global dump 1,
   *          ...
   *          sum of X:B in all 'browser' process dumps in global dump N
   *        ]
   *
   *    memory:chrome:browser_process:source:X:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A+X:B in all 'browser' process dumps in global dump 1,
   *          ...
   *          sum of X:A+X:B in all 'browser' process dumps in global dump N
   *        ]
   *
   *    memory:chrome:browser_process:source:Y:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of Y in all 'browser' process dumps in global dump 1,
   *          ...
   *          sum of Y in all 'browser' process dumps in global dump N
   *        ]
   *
   *    memory:chrome:browser_process:source:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A+X:B+Y in all 'browser' process dumps in global dump 1,
   *          ...
   *          sum of X:A+X:B+Y in all 'browser' process dumps in global dump N
   *        ]
   *
   *    ...
   *
   *    memory:chrome:all_processes:source:X:A:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A in all process dumps in global dump 1,
   *          ...
   *          sum of X:A in all process dumps in global dump N,
   *    ]
   *
   *    memory:chrome:all_processes:source:X:B:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:B in all process dumps in global dump 1,
   *          ...
   *          sum of X:B in all process dumps in global dump N,
   *    ]
   *
   *    memory:chrome:all_processes:source:X:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A+X:B in all process dumps in global dump 1,
   *          ...
   *          sum of X:A+X:B in all process dumps in global dump N,
   *    ]
   *
   *    memory:chrome:all_processes:source:Y:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of Y in all process dumps in global dump 1,
   *          ...
   *          sum of Y in all process dumps in global dump N
   *    ]
   *
   *    memory:chrome:all_processes:source:proportional_resident_size :
   *        Histogram aggregated over [
   *          sum of X:A+X:B+Y in all process dumps in global dump 1,
   *          ...
   *          sum of X:A+X:B+Y in all process dumps in global dump N
   *        ]
   *
   * where global dumps 1 to N are the global dumps associated with the given
   * browser.
   *
   * @param {!Map<string, !Array<!tr.model.GlobalMemoryDump>}
   *     browserNameToGlobalDumps Map from browser names to arrays of global
   *     memory dumps. The generic values will be extracted from the associated
   *     process memory dumps.
   * @param {!function(!tr.model.GlobalMemoryDump): boolean}
   *     customGlobalDumpFilter Predicate for filtering global memory dumps.
   * @param {!function(
   *     !tr.model.ProcessMemoryDump,
   *     !function(!{
   *         source: string,
   *         componentPath: (!Array<string>|undefined),
   *         property: !{name: string, unit: !tr.b.Unit, buildDescriptionPrefix:
   *                     !function(!Array<string>, string): string},
   *         value: (!tr.v.Histogram|number|undefined)
   *     }))}
   *     customProcessDumpValueExtractor Callback for extracting values from a
   *     process memory dump.
   * @param {!function(!tr.b.MultiDimensionalViewNode)}
   *     customComponentTreeModifier Callback applied to every component tree
   *     wrt each process name.
   * @param {!tr.v.HistogramSet} values List of values to which the
   *     resulting aggregated values are added.
   */
  function addMemoryDumpValues(browserNameToGlobalDumps, customGlobalDumpFilter,
      customProcessDumpValueExtractor, customComponentTreeModifier,
      values) {
    browserNameToGlobalDumps.forEach(function(globalDumps, browserName) {
      const filteredGlobalDumps = globalDumps.filter(customGlobalDumpFilter);
      const sourceToPropertyToBuilder = extractDataFromGlobalDumps(
          filteredGlobalDumps, customProcessDumpValueExtractor);
      reportDataAsValues(sourceToPropertyToBuilder, browserName,
          customComponentTreeModifier, values);
    });
  }

  /**
   * For each global memory dump in |globalDumps|, calculate per-process-name
   * sums of values extracted by |customProcessDumpValueExtractor| from the
   * associated process memory dumps.
   *
   * This function returns the following nested map structure:
   *
   *  Source name (Map key, e.g. 'reported_by_os')
   *    -> Property (Map key, e.g. PROPORTIONAL_RESIDENT_SIZE)
   *      -> processAndComponentTreeBuilder
   *
   *  where |processAndComponentTreeBuilder| is a
   *  tr.b.MultiDimensionalViewBuilder:
   *
   *  Process name (0th dimension key, e.g. 'browser_process') x
   *  Component path (1st dimension keys, e.g. ['system', 'native_heap'])
   *    -> Sum of value over the processes (number).
   *
   * See addMemoryDumpValues for more details.
   */
  function extractDataFromGlobalDumps(
      globalDumps, customProcessDumpValueExtractor) {
    const sourceToPropertyToBuilder = new Map();
    const dumpCount = globalDumps.length;
    globalDumps.forEach(function(globalDump, dumpIndex) {
      for (const processDump of Object.values(globalDump.processMemoryDumps)) {
        extractDataFromProcessDump(
            processDump, sourceToPropertyToBuilder, dumpIndex, dumpCount,
            customProcessDumpValueExtractor);
      }
    });
    return sourceToPropertyToBuilder;
  }

  function extractDataFromProcessDump(processDump, sourceToPropertyToBuilder,
      dumpIndex, dumpCount, customProcessDumpValueExtractor) {
    // Process name is typically 'browser', 'renderer', etc.
    const rawProcessName = processDump.process.name;
    const processNamePath =
        [tr.e.chrome.chrome_processes.canonicalizeProcessName(rawProcessName)];

    customProcessDumpValueExtractor(
        processDump,
        function addProcessScalar(spec) {
          if (spec.value === undefined) return;

          const component = spec.component || [];
          function createDetailsForErrorMessage() {
            return ['source=', spec.source, ', property=',
              spec.property.name || '(undefined)', ', component=',
              component.length === 0 ? '(empty)' : component.join(':'),
              ' in ', processDump.process.userFriendlyName].join('');
          }

          let value;
          if (spec.value instanceof tr.b.Scalar) {
            value = spec.value.value;
            if (spec.value.unit !== spec.property.unit) {
              throw new Error('Scalar unit for ' +
                  createDetailsForErrorMessage() + ' (' +
                  spec.value.unit.unitName +
                  ') doesn\'t match the unit of the property (' +
                  spec.property.unit.unitName + ')');
            }
          } else {
            value = spec.value;
          }

          let propertyToBuilder = sourceToPropertyToBuilder.get(spec.source);
          if (propertyToBuilder === undefined) {
            propertyToBuilder = new Map();
            sourceToPropertyToBuilder.set(spec.source, propertyToBuilder);
          }

          let builder = propertyToBuilder.get(spec.property);
          if (builder === undefined) {
            builder = new tr.b.MultiDimensionalViewBuilder(
                2 /* dimensions (process name and component path) */,
                dumpCount /* valueCount */),
            propertyToBuilder.set(spec.property, builder);
          }

          const values = new Array(dumpCount);
          values[dumpIndex] = value;

          builder.addPath(
              [processNamePath, component] /* path */, values,
              tr.b.MultiDimensionalViewBuilder.ValueKind.TOTAL /* valueKind */);
        });
  }

  function reportDataAsValues(sourceToPropertyToBuilder, browserName,
      customComponentTreeModifier, values) {
    // For each source name (e.g. 'reported_by_os')...
    sourceToPropertyToBuilder.forEach(function(propertyToBuilder, sourceName) {
      // For each property (e.g. EFFECTIVE_SIZE)...
      propertyToBuilder.forEach(function(builders, property) {
        const tree = builders.buildTopDownTreeView();
        reportComponentDataAsValues(browserName, sourceName, property,
            [] /* processPath */, [] /* componentPath */, tree, values,
            customComponentTreeModifier);
      });
    });
  }

  /**
   * For the given |browserName| (e.g. 'chrome'), |property|
   * (e.g. EFFECTIVE_SIZE), |processPath| (e.g. ['browser_process']),
   * |componentPath| (e.g. ['v8']), add
   * a tr.v.Histogram with |unit| aggregating the total
   * values of the associated |componentNode| across all timestamps
   * (corresponding to global memory dumps associated with the given browser)
   * |values| for each process (e.g. 'gpu_process', 'browser_process', etc).
   * We also report a special 'all_processes' histogram which agregates all
   * others, this has a RelatedNameMap diagnostic explaining
   * how it is built from the other histograms.
   *
   * See addMemoryDumpValues for more details.
   */
  function reportComponentDataAsValues(browserName, sourceName, property,
      processPath, componentPath, tree, values, customComponentTreeModifier,
      opt_cachedHistograms) {
    const cachedHistograms = opt_cachedHistograms || new Map();
    function recurse(processPath, componentPath, node) {
      return reportComponentDataAsValues(browserName, sourceName, property,
          processPath, componentPath, node, values,
          customComponentTreeModifier, cachedHistograms);
    }

    function buildHistogram(processPath, componentPath, node) {
      return buildNamedMemoryNumericFromNode(
          browserName,
          sourceName,
          property,
          processPath.length === 0 ? 'all_processes' : processPath[0],
          componentPath,
          node);
    }

    customComponentTreeModifier(tree);
    const histogram = buildHistogram(processPath, componentPath, tree);
    if (cachedHistograms.has(histogram.name)) {
      return cachedHistograms.get(histogram.name);
    }
    cachedHistograms.set(histogram.name, histogram);

    const processNames = new tr.v.d.RelatedNameMap();
    for (const [childProcessName, childProcessNode] of tree.children[0]) {
      processPath.push(childProcessName);
      const childProcessHistogram =
        recurse(processPath, componentPath, childProcessNode);
      processNames.set(childProcessName, childProcessHistogram.name);
      processPath.pop();
    }

    const componentNames = new tr.v.d.RelatedNameMap();
    for (const [childComponentName, childComponentNode] of tree.children[1]) {
      componentPath.push(childComponentName);
      const childComponentHistogram =
        recurse(processPath, componentPath, childComponentNode);
      componentNames.set(childComponentName, childComponentHistogram.name);
      componentPath.pop();
    }

    values.addHistogram(histogram);
    if (tree.children[0].size > 0) {
      histogram.diagnostics.set('processes', processNames);
    }
    if (tree.children[1].size > 0) {
      histogram.diagnostics.set('components', componentNames);
    }

    return histogram;
  }

  /**
   * Gets the name for a histogram.
   * The histograms have the following naming scheme:
   * memory:chrome:browser_process:reported_by_chrome:v8:heap:effective_size_avg
   *        ^browser ^process      ^source            ^component  ^property
   */
  function getNumericName(
      browserName, sourceName, propertyName, processName, componentPath) {
    // Construct the name of the memory value.
    const nameParts = ['memory', browserName, processName, sourceName].concat(
        componentPath);
    if (propertyName !== undefined) nameParts.push(propertyName);
    return nameParts.join(':');
  }

  /**
   * Gets the description of a histogram.
   */
  function getNumericDescription(
      property, browserName, processName, componentPath) {
    return [
      property.buildDescriptionPrefix(componentPath, processName),
      'in',
      convertBrowserNameToUserFriendlyName(browserName)
    ].join(' ');
  }

  /**
   * Create a memory tr.v.Histogram with |unit| and add all total values in
   * |node| to it. Names and describes the histogram according to the
   * |browserName|, |sourceName|, |property|, |processName| and
   * |componentPath|.
   */
  function buildNamedMemoryNumericFromNode(
      browserName, sourceName, property, processName, componentPath, node) {
    const name = getNumericName(
        browserName, sourceName, property.name, processName, componentPath);
    const description = getNumericDescription(
        property, browserName, processName, componentPath);

    // Build the underlying numeric for the memory value.
    const numeric = buildMemoryNumericFromNode(name, node, property.unit);
    numeric.description = description;
    return numeric;
  }

  function buildSampleDiagnostics(value, node) {
    if (node.children.length < 2) return undefined;
    const diagnostics = new Map();
    const i = node.values.indexOf(value);

    const processBreakdown = new tr.v.d.Breakdown();
    processBreakdown.colorScheme =
      tr.e.chrome.chrome_processes.PROCESS_COLOR_SCHEME_NAME;
    for (const [name, subNode] of node.children[0]) {
      processBreakdown.set(name, subNode.values[i].total);
    }
    if (processBreakdown.size > 0) {
      diagnostics.set('processes', processBreakdown);
    }

    const componentBreakdown = new tr.v.d.Breakdown();
    for (const [name, subNode] of node.children[1]) {
      componentBreakdown.set(name, subNode.values[i].total);
    }
    if (componentBreakdown.size > 0) {
      diagnostics.set('components', componentBreakdown);
    }

    if (diagnostics.size === 0) return undefined;
    return diagnostics;
  }

  /**
   * Create a memory tr.v.Histogram with |unit| and add all total values in
   * |node| to it.
   */
  function buildMemoryNumericFromNode(name, node, unit) {
    const histogram = new tr.v.Histogram(
        name, unit, BOUNDARIES_FOR_UNIT_MAP.get(unit));

    node.values.forEach(v => histogram.addSample(
        v.total, buildSampleDiagnostics(v, node)));

    return histogram;
  }

  tr.metrics.MetricRegistry.register(memoryMetric, {
    supportsRangeOfInterest: true
  });

  return {
    memoryMetric,
  };
});
</script>