Update performance.measureMemory to the latest spec

The result of a memory measurement now:
- includes an empty breakdown entry.
- has random order of breakdown entryies.

Bug: chromium:1085129
Change-Id: Ie3f338d8274a0276d09f732560ed9797f5c376af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2607339
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841002}

third_party/blink/renderer/core/timing/measure_memory/measure_memory_controller.cc

@@ -4,6 +4,8 @@
 
 #include "third_party/blink/renderer/core/timing/measure_memory/measure_memory_controller.h"
 
+#include <algorithm>
+#include "base/rand_util.h"
 #include "components/performance_manager/public/mojom/coordination_unit.mojom-blink.h"
 #include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/platform/platform.h"
@@ -112,6 +114,19 @@ bool MeasureMemoryController::IsMeasureMemoryAvailable(LocalDOMWindow* window) {
 
 namespace {
 
+// Satisfies the requirements of UniformRandomBitGenerator from C++ standard.
+// It is used in std::shuffle calls below.
+struct RandomBitGenerator {
+  using result_type = size_t;
+  static constexpr size_t min() { return 0; }
+  static constexpr size_t max() {
+    return static_cast<size_t>(std::numeric_limits<int>::max());
+  }
+  size_t operator()() {
+    return static_cast<size_t>(base::RandInt(min(), max()));
+  }
+};
+
 // These functions convert WebMemory* mojo structs to IDL and JS values.
 WTF::String ConvertScope(WebMemoryAttribution::Scope scope) {
   using Scope = WebMemoryAttribution::Scope;
@@ -141,7 +156,15 @@ MemoryBreakdownEntry* ConvertBreakdown(
     attribution.push_back(ConvertAttribution(entry));
   }
   result->setAttribution(attribution);
-  result->setUserAgentSpecificTypes(Vector<String>());
+  result->setUserAgentSpecificTypes({});
+  return result;
+}
+
+MemoryBreakdownEntry* EmptyBreakdown() {
+  auto* result = MemoryBreakdownEntry::Create();
+  result->setBytes(0);
+  result->setAttribution({});
+  result->setUserAgentSpecificTypes({});
   return result;
 }
 
@@ -150,6 +173,11 @@ MemoryMeasurement* ConvertResult(const WebMemoryMeasurementPtr& measurement) {
   for (const auto& entry : measurement->breakdown) {
     breakdown.push_back(ConvertBreakdown(entry));
   }
+  // Add an empty breakdown entry as required by the spec.
+  // See https://github.com/WICG/performance-measure-memory/issues/10.
+  breakdown.push_back(EmptyBreakdown());
+  // Randomize the order of the entries as required by the spec.
+  std::shuffle(breakdown.begin(), breakdown.end(), RandomBitGenerator{});
   size_t bytes = 0;
   for (auto entry : breakdown) {
     bytes += entry->bytes();

third_party/blink/web_tests/android/ChromiumWPTExpectations

@@ -3157,6 +3157,7 @@ crbug.com/1050754 external/wpt/measure-memory/window-open.cross-origin.tentative
 crbug.com/1050754 external/wpt/measure-memory/window-open.cross-site.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.mix.tentative.https.window.html [ Failure Timeout ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.same-origin.tentative.https.window.html [ Failure ]
+crbug.com/1050754 external/wpt/measure-memory/randomized-breakdown.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.worker.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/encodingInfo.html [ Failure Pass ]

third_party/blink/web_tests/android/WeblayerWPTExpectations

@@ -3137,6 +3137,7 @@ crbug.com/1050754 external/wpt/measure-memory/window-open.cross-origin.tentative
 crbug.com/1050754 external/wpt/measure-memory/window-open.cross-site.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.mix.tentative.https.window.html [ Failure Timeout ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.same-origin.tentative.https.window.html [ Failure ]
+crbug.com/1050754 external/wpt/measure-memory/randomized-breakdown.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.worker.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/encodingInfo.html [ Failure ]

third_party/blink/web_tests/android/WebviewWPTExpectations

@@ -3384,6 +3384,7 @@ crbug.com/1050754 external/wpt/measure-memory/window-open.cross-origin.tentative
 crbug.com/1050754 external/wpt/measure-memory/window-open.cross-site.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.mix.tentative.https.window.html [ Failure Timeout ]
 crbug.com/1050754 external/wpt/measure-memory/window-open.same-origin.tentative.https.window.html [ Failure ]
+crbug.com/1050754 external/wpt/measure-memory/randomized-breakdown.tentative.https.window.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/decodingInfo.any.worker.html [ Failure ]
 crbug.com/1050754 external/wpt/media-capabilities/encodingInfo.html [ Failure ]

third_party/blink/web_tests/external/wpt/measure-memory/randomized-breakdown.tentative.https.window.js

+// META: script=/common/get-host-info.sub.js
+// META: script=./resources/common.js
+// META: timeout=long
+'use strict';
+
+function indexOfEmptyEntry(result) {
+  return result.breakdown.findIndex(isEmptyBreakdownEntry);
+}
+
+assert_true(self.crossOriginIsolated);
+promise_test(async testCase => {
+  const initial = await performance.measureMemory();
+  let observed_different_order = false;
+  for (let i = 0; i < 100; ++i) {
+    const current = await performance.measureMemory();
+    if (indexOfEmptyEntry(initial) != indexOfEmptyEntry(current)) {
+      observed_different_order = true;
+    }
+  }
+  // The order of the breakdown entries must be randomized.
+  // A conforming implementation may fail the following assert with
+  // the probability of at most 2^-100 since there are at least two
+  // entries in the breakdown.
+  assert_true(observed_different_order);
+}, 'Well-formed result of performance.measureMemory.');

third_party/blink/web_tests/external/wpt/measure-memory/randomized-breakdown.tentative.https.window.js.headers

+Cross-Origin-Opener-Policy: same-origin
+Cross-Origin-Embedder-Policy: require-corp
\ No newline at end of file

third_party/blink/web_tests/external/wpt/measure-memory/resources/common.js

@@ -39,6 +39,11 @@ function checkBreakdown(breakdown, expected) {
   }
 }
 
+function isEmptyBreakdownEntry(entry) {
+  return entry.bytes === 0 && entry.attribution.length === 0 &&
+         entry.userAgentSpecificTypes.length === 0;
+}
+
 function checkMeasureMemory(result, expected) {
   assert_own_property(result, 'bytes');
   assert_own_property(result, 'breakdown');
@@ -54,6 +59,8 @@ function checkMeasureMemory(result, expected) {
           JSON.stringify(e) + ' did not appear in the result.');
     }
   }
+  assert_true(result.breakdown.some(isEmptyBreakdownEntry),
+      'The result must include an empty breakdown entry.');
 }
 
 function url(params) {