Make WindowPerformanceTest use one object-under-test

WindowPerformanceTest exists to check the behaviour of WindowPerformance
instances. It used to mock a page with DummyPageHolder (which, by way of
a LocalDOMWindow, would end up owning a WindowPerformance instance) as
well as construct its own WindowPerformance instance. This lead to the
mock objects referring to a separate, intrinsic WindowPerformance than
the one being directly manipulated by the tests.

This change removes the one-off constructed WindowPerformance and
exercises the WindowPerformance from the mock objects instead.

Change-Id: I90980074362c36b630252a82f58b973ae1963965
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1965942Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Tom McKee <tommckee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728547}

third_party/blink/renderer/core/timing/window_performance_test.cc

@@ -80,8 +80,9 @@ class WindowPerformanceTest : public testing::Test {
   void ResetPerformance() {
     page_holder_ = std::make_unique<DummyPageHolder>(IntSize(800, 600));
     page_holder_->GetDocument().SetURL(KURL("https://example.com"));
-    performance_ = MakeGarbageCollected<WindowPerformance>(
-        page_holder_->GetDocument().domWindow());
+
+    LocalDOMWindow* window = LocalDOMWindow::From(GetScriptState());
+    performance_ = DOMWindowPerformance::performance(*window);
     unified_clock_ = std::make_unique<Performance::UnifiedClock>(
         test_task_runner_->GetMockClock(),
         test_task_runner_->GetMockTickClock());
@@ -89,6 +90,10 @@ class WindowPerformanceTest : public testing::Test {
     performance_->time_origin_ = GetTimeOrigin();
   }
 
+  ScriptState* GetScriptState() const {
+    return ToScriptStateForMainWorld(page_holder_->GetDocument().GetFrame());
+  }
+
   Persistent<WindowPerformance> performance_;
   std::unique_ptr<DummyPageHolder> page_holder_;
   scoped_refptr<base::TestMockTimeTaskRunner> test_task_runner_;
@@ -190,7 +195,10 @@ TEST(PerformanceLifetimeTest, SurviveContextSwitch) {
 // Make sure the output entries with the same timestamps follow the insertion
 // order. (http://crbug.com/767560)
 TEST_F(WindowPerformanceTest, EnsureEntryListOrder) {
-  V8TestingScope scope;
+  // Need to have an active V8 context for ScriptValues to operate.
+  v8::HandleScope handle_scope(GetScriptState()->GetIsolate());
+  v8::Local<v8::Context> context = GetScriptState()->GetContext();
+  v8::Context::Scope context_scope(context);
   auto initial_offset =
       test_task_runner_->NowTicks().since_origin().InSecondsF();
   test_task_runner_->FastForwardBy(GetTimeOrigin() - base::TimeTicks());
@@ -198,12 +206,12 @@ TEST_F(WindowPerformanceTest, EnsureEntryListOrder) {
   DummyExceptionStateForTesting exception_state;
   test_task_runner_->FastForwardBy(base::TimeDelta::FromSeconds(2));
   for (int i = 0; i < 8; i++) {
-    performance_->mark(scope.GetScriptState(), AtomicString::Number(i), nullptr,
+    performance_->mark(GetScriptState(), AtomicString::Number(i), nullptr,
                        exception_state);
   }
   test_task_runner_->FastForwardBy(base::TimeDelta::FromSeconds(2));
   for (int i = 8; i < 17; i++) {
-    performance_->mark(scope.GetScriptState(), AtomicString::Number(i), nullptr,
+    performance_->mark(GetScriptState(), AtomicString::Number(i), nullptr,
                        exception_state);
   }
   PerformanceEntryVector entries = performance_->getEntries();