cc: Make SingleThreadProxy ignore commit requests inside Layout().

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index c25ed4d1dbb6d5f48337e29594a8044f09eab369..b9f6a4849131dfa14431b6f7a0b48dd4fe81fab9 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -50,11 +50,21 @@ SingleThreadProxy::SingleThreadProxy(
       commit_requested_(false),
       inside_synchronous_composite_(false),
       output_surface_creation_requested_(false),
-      external_begin_frame_source_(external_begin_frame_source.Pass()),
       weak_factory_(this) {
   TRACE_EVENT0("cc", "SingleThreadProxy::SingleThreadProxy");
   DCHECK(Proxy::IsMainThread());
   DCHECK(layer_tree_host);
+
+  if (layer_tree_host->settings().single_thread_proxy_scheduler &&
+      !scheduler_on_impl_thread_) {
+    SchedulerSettings scheduler_settings(
+        layer_tree_host->settings().ToSchedulerSettings());
+    // SingleThreadProxy should run in main thread low latency mode.
+    scheduler_settings.main_thread_should_always_be_low_latency = true;
+    scheduler_on_impl_thread_ = Scheduler::Create(
+        this, scheduler_settings, layer_tree_host_->id(),
+        MainThreadTaskRunner(), external_begin_frame_source.Pass());
+  }
 }
 
 void SingleThreadProxy::Start() {
@@ -95,18 +105,7 @@ void SingleThreadProxy::SetLayerTreeHostClientReady() {
   // nothing to do.
   DCHECK(Proxy::IsMainThread());
   DebugScopedSetImplThread impl(this);
-  if (layer_tree_host_->settings().single_thread_proxy_scheduler &&
-      !scheduler_on_impl_thread_) {
-    SchedulerSettings scheduler_settings(
-        layer_tree_host_->settings().ToSchedulerSettings());
-    // SingleThreadProxy should run in main thread low latency mode.
-    scheduler_settings.main_thread_should_always_be_low_latency = true;
-    scheduler_on_impl_thread_ =
-        Scheduler::Create(this,
-                          scheduler_settings,
-                          layer_tree_host_->id(),
-                          MainThreadTaskRunner(),
-                          external_begin_frame_source_.Pass());
+  if (scheduler_on_impl_thread_) {
     scheduler_on_impl_thread_->SetCanStart();
     scheduler_on_impl_thread_->SetVisible(layer_tree_host_impl_->visible());
   }
@@ -214,7 +213,6 @@ void SingleThreadProxy::DoCommit() {
   // fixed.
   tracked_objects::ScopedTracker tracking_profile1(
       FROM_HERE_WITH_EXPLICIT_FUNCTION("461509 SingleThreadProxy::DoCommit1"));
-  commit_requested_ = false;
   layer_tree_host_->WillCommit();
   devtools_instrumentation::ScopedCommitTrace commit_task(
       layer_tree_host_->id());
@@ -334,8 +332,10 @@ void SingleThreadProxy::CommitComplete() {
 
 void SingleThreadProxy::SetNeedsCommit() {
   DCHECK(Proxy::IsMainThread());
-  DebugScopedSetImplThread impl(this);
   client_->ScheduleComposite();
+  if (commit_requested_)
+    return;
+  DebugScopedSetImplThread impl(this);
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->SetNeedsCommit();
   commit_requested_ = true;
@@ -766,7 +766,11 @@ void SingleThreadProxy::DidCommitAndDrawFrame() {
 }
 
 bool SingleThreadProxy::MainFrameWillHappenForTesting() {
-  return false;
+  if (layer_tree_host_->output_surface_lost())
+    return false;
+  if (!scheduler_on_impl_thread_)
+    return false;
+  return scheduler_on_impl_thread_->MainFrameForTestingWillHappen();
 }
 
 void SingleThreadProxy::SetChildrenNeedBeginFrames(
@@ -804,6 +808,8 @@ void SingleThreadProxy::SendBeginMainFrameNotExpectedSoon() {
 }
 
 void SingleThreadProxy::BeginMainFrame() {
+  commit_requested_ = false;
+
   if (defer_commits_) {
     TRACE_EVENT_INSTANT0("cc", "EarlyOut_DeferCommit",
                          TRACE_EVENT_SCOPE_THREAD);
@@ -831,6 +837,9 @@ void SingleThreadProxy::BeginMainFrame() {
     return;
   }
 
+  // Prevent new commits from being requested inside DoBeginMainFrame.
+  commit_requested_ = true;
+
   const BeginFrameArgs& begin_frame_args =
       layer_tree_host_impl_->CurrentBeginFrameArgs();
   DoBeginMainFrame(begin_frame_args);
@@ -855,6 +864,9 @@ void SingleThreadProxy::DoBeginMainFrame(
   DCHECK(!queue_for_commit_);
   queue_for_commit_ = make_scoped_ptr(new ResourceUpdateQueue);
 
+  // New commits requested inside UpdateLayers should be respected.
+  commit_requested_ = false;
+
   layer_tree_host_->UpdateLayers(queue_for_commit_.get());
 
   timing_history_.DidBeginMainFrame();