[scheduler] Issue RequestBeginMainFrameNotExpected call asynchronously.

Post a control task to call RequestBeginMainFrameNotExpected
asynchronously to avoid calling it when frame tree is dirty.

R=yutak@chromium.org,dcheng@chromium.org,haraken@chromium.org
BUG=820893

Change-Id: I375aa46180f20f053c13563df910d3813c22938f
Reviewed-on: https://chromium-review.googlesource.com/962787Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543683}

third_party/WebKit/Source/core/page/Page.cpp

@@ -802,15 +802,6 @@ void Page::RequestBeginMainFrameNotExpected(bool new_state) {
     return;
 
   if (LocalFrame* main_frame = DeprecatedLocalMainFrame()) {
-    if (!main_frame->Client()) {
-      // This can happen while swapping out web frames because the scheduler can
-      // be invoked in the middle of Oilpan allocation.
-      // TODO(https://crbug.com/820893): Figure out how to avoid this
-      // complicated corner case. As written, it's not clear PageScheduler
-      // does this correctly for OOPIF anyway since it only talks to the root
-      // WebLayerTreeView, but a page with OOPIFs also has local roots.
-      return;
-    }
     if (WebLayerTreeView* layer_tree_view =
             chrome_client_->GetWebLayerTreeView(main_frame)) {
       layer_tree_view->RequestBeginMainFrameNotExpected(new_state);

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

@@ -2228,11 +2228,29 @@ void RendererSchedulerImpl::OnPendingTasksChanged(bool has_tasks) {
       main_thread_only().compositor_will_send_main_frame_not_expected.get())
     return;
 
+  // Dispatch RequestBeginMainFrameNotExpectedSoon notifications asynchronously.
+  // This is needed because idle task can be posted (and OnPendingTasksChanged
+  // called) at any moment, including in the middle of allocating an object,
+  // when state is not consistent. Posting a task to dispatch notifications
+  // minimizes the amount of code that runs and sees an inconsistent state .
+  control_task_queue_->PostTask(
+      FROM_HERE,
+      base::BindOnce(
+          &RendererSchedulerImpl::DispatchRequestBeginMainFrameNotExpected,
+          weak_factory_.GetWeakPtr(), has_tasks));
+}
+
+void RendererSchedulerImpl::DispatchRequestBeginMainFrameNotExpected(
+    bool has_tasks) {
+  if (has_tasks ==
+      main_thread_only().compositor_will_send_main_frame_not_expected.get())
+    return;
   main_thread_only().compositor_will_send_main_frame_not_expected = has_tasks;
 
-  TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "RendererSchedulerImpl::OnPendingTasksChanged", "has_tasks",
-               has_tasks);
+  TRACE_EVENT1(
+      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
+      "RendererSchedulerImpl::DispatchRequestBeginMainFrameNotExpected",
+      "has_tasks", has_tasks);
   for (PageSchedulerImpl* page_scheduler : main_thread_only().page_schedulers) {
     page_scheduler->RequestBeginMainFrameNotExpected(has_tasks);
   }

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.h

@@ -484,6 +484,7 @@ class PLATFORM_EXPORT RendererSchedulerImpl
   void OnIdlePeriodEnded() override;
 
   void OnPendingTasksChanged(bool has_tasks) override;
+  void DispatchRequestBeginMainFrameNotExpected(bool has_tasks);
 
   void EndIdlePeriod();
 

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl_unittest.cc

@@ -34,6 +34,8 @@ namespace scheduler {
 // To avoid symbol collisions in jumbo builds.
 namespace renderer_scheduler_impl_unittest {
 
+using ::testing::Mock;
+
 class FakeInputEvent : public blink::WebInputEvent {
  public:
   explicit FakeInputEvent(blink::WebInputEvent::Type event_type,
@@ -207,9 +209,10 @@ class ScopedAutoAdvanceNowEnabler {
 
 class RendererSchedulerImplForTest : public RendererSchedulerImpl {
  public:
+  using RendererSchedulerImpl::EstimateLongestJankFreeTaskDuration;
   using RendererSchedulerImpl::OnIdlePeriodEnded;
   using RendererSchedulerImpl::OnIdlePeriodStarted;
-  using RendererSchedulerImpl::EstimateLongestJankFreeTaskDuration;
+  using RendererSchedulerImpl::OnPendingTasksChanged;
 
   RendererSchedulerImplForTest(std::unique_ptr<TaskQueueManager> manager,
                                base::Optional<base::Time> initial_virtual_time)
@@ -3258,6 +3261,8 @@ class PageSchedulerImplForTest : public PageSchedulerImpl {
     return interventions_;
   }
 
+  MOCK_METHOD1(RequestBeginMainFrameNotExpected, void(bool));
+
  private:
   std::vector<std::string> interventions_;
 
@@ -4161,6 +4166,40 @@ TEST_F(RendererSchedulerImplTest, LoadingControlTasks) {
                                    std::string("L5"), std::string("L6")));
 }
 
+TEST_F(RendererSchedulerImplTest, RequestBeginMainFrameNotExpected) {
+  std::unique_ptr<PageSchedulerImplForTest> page_scheduler =
+      std::make_unique<PageSchedulerImplForTest>(scheduler_.get());
+  scheduler_->AddPageScheduler(page_scheduler.get());
+
+  scheduler_->OnPendingTasksChanged(true);
+  EXPECT_CALL(*page_scheduler, RequestBeginMainFrameNotExpected(true)).Times(1);
+  RunUntilIdle();
+
+  Mock::VerifyAndClearExpectations(page_scheduler.get());
+
+  scheduler_->OnPendingTasksChanged(false);
+  EXPECT_CALL(*page_scheduler, RequestBeginMainFrameNotExpected(false))
+      .Times(1);
+  RunUntilIdle();
+
+  Mock::VerifyAndClearExpectations(page_scheduler.get());
+}
+
+TEST_F(RendererSchedulerImplTest,
+       RequestBeginMainFrameNotExpected_MultipleCalls) {
+  std::unique_ptr<PageSchedulerImplForTest> page_scheduler =
+      std::make_unique<PageSchedulerImplForTest>(scheduler_.get());
+  scheduler_->AddPageScheduler(page_scheduler.get());
+
+  scheduler_->OnPendingTasksChanged(true);
+  scheduler_->OnPendingTasksChanged(true);
+  // Multiple calls should result in only one call.
+  EXPECT_CALL(*page_scheduler, RequestBeginMainFrameNotExpected(true)).Times(1);
+  RunUntilIdle();
+
+  Mock::VerifyAndClearExpectations(page_scheduler.get());
+}
+
 #if defined(OS_ANDROID)
 TEST_F(RendererSchedulerImplTest, PauseTimersForAndroidWebView) {
   ScopedAutoAdvanceNowEnabler enable_auto_advance_now(mock_task_runner_);