Compute-Pressure: Initial web API for reporting compute pressure

This tracks the initial blink implementation of the compute pressure API.
The interface presented in this CL follows the EventEmitter pattern.

Events will be emitted periodically after the developer has requested
that compute data be sent via the API.

Fixed: 1183600
Change-Id: I4fd929950b2a0d7810780e5af8d85063f4a3c6e3

compute-pressure/README.md

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+This directory contains (tentative) tests for the
+[Compute Pressure](https://oyiptong.github.io/compute-pressure/) specification.

compute-pressure/compute_pressure.tentative.https.window.js

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+// META: script=/resources/testdriver.js
+// META: script=/resources/testdriver-vendor.js
+// META: script=resources/utils.js
+
+'use strict';
+
+compute_pressure_test(async t => {
+  const obs = await navigator.deviceCompute.query();
+  await new Promise(resolve => {
+    obs.addEventListener('update', event => {
+      assert_true((typeof event.cpuUtilization == 'number'));
+      assert_true((typeof event.cpuSpeedLimit == 'number'));
+      assert_greater_than_equal(
+          event.cpuUtilization, 0,
+          'CPU Utilization is greater or equal to zero');
+      assert_greater_than_equal(
+          event.cpuSpeedLimit, 0,
+          'CPU Utilization is greater or equal to zero');
+      resolve();
+    });
+  });
+}, 'query(): returns an EventTarget that fires an "update" event with CPU data');

compute-pressure/resources/utils.js

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+'use strict';
+
+function isPlatformSupported() {
+  if (navigator.platform.indexOf('Android') != -1 ||
+      navigator.platform.indexOf('Linux') != -1) {
+    return true;
+  }
+  return false;
+}
+
+function compute_pressure_test(test_function, name, properties) {
+  return promise_test(async (t) => {
+    if (!isPlatformSupported()) {
+      await promise_rejects_dom(
+          t, 'NotSupportedError', navigator.deviceCompute.query());
+      return;
+    }
+    await test_function(t, name, properties);
+  });
+}