Trace.js

// @flow
import type {Profile} from './Profiler';
import type {Writable} from 'stream';
import {Tracer} from 'chrome-trace-event';

export default class Trace {
  tracer: Tracer;
  tid: number;
  eventId: number;

  constructor() {
    this.tracer = new Tracer();
    this.tid = 0;
    this.eventId = 0;
    this.init();
  }

  getEventId() {
    return this.eventId++;
  }

  init() {
    this.tracer.instantEvent({
      name: 'TracingStartedInPage',
      id: this.getEventId(),
      cat: ['disabled-by-default-devtools.timeline'],
      args: {
        data: {
          sessionId: '-1',
          page: '0xfff',
          frames: [
            {
              frame: '0xfff',
              url: 'parcel',
              name: '',
            },
          ],
        },
      },
    });

    this.tracer.instantEvent({
      name: 'TracingStartedInBrowser',
      id: this.getEventId(),
      cat: ['disabled-by-default-devtools.timeline'],
      args: {
        data: {
          sessionId: '-1',
        },
      },
    });
  }

  addCPUProfile(name: string, profile: Profile) {
    const trace = this.tracer;
    const tid = this.tid;
    this.tid++;

    const cpuStartTime = profile.startTime;
    const cpuEndTime = profile.endTime;

    trace.instantEvent({
      tid,
      id: this.getEventId(),
      cat: ['toplevel'],
      name: 'TaskQueueManager::ProcessTaskFromWorkQueue',
      args: {
        src_file: '../../ipc/ipc_moji_bootstrap.cc',
        src_func: 'Accept',
      },
      ts: cpuStartTime,
    });

    trace.completeEvent({
      tid,
      name: 'EvaluateScript',
      id: this.getEventId(),
      cat: ['devtools.timeline'],
      ts: cpuStartTime,
      dur: cpuEndTime - cpuStartTime,
      args: {
        data: {
          url: 'parcel',
          lineNumber: 1,
          columnNumber: 1,
          frame: '0xFFF',
        },
      },
    });

    trace.instantEvent({
      tid,
      ts: 0,
      ph: 'M',
      cat: ['__metadata'],
      name: 'thread_name',
      args: {name},
    });

    trace.instantEvent({
      tid,
      name: 'CpuProfile',
      id: this.getEventId(),
      cat: ['disabled-by-default-devtools.timeline'],
      ts: cpuEndTime,
      args: {
        data: {
          cpuProfile: profile,
        },
      },
    });
  }

  pipe(writable: Writable) {
    return this.tracer.pipe(writable);
  }

  flush() {
    this.tracer.push(null);
  }
}