Revert of Make ui::Compositor use ui::Scheduler

cc/trees/single_thread_proxy.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "cc/debug/benchmark_instrumentation.h"
 #include "cc/output/context_provider.h"
@@ skipping 72 matching lines @@
 
 void SingleThreadProxy::SetLayerTreeHostClientReady() {
   TRACE_EVENT0("cc", "SingleThreadProxy::SetLayerTreeHostClientReady");
   // Scheduling is controlled by the embedder in the single thread case, so
   // 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());
-    // 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(),
                           base::PowerMonitor::Get(),
                           external_begin_frame_source_.Pass());
     scheduler_on_impl_thread_->SetCanStart();
     scheduler_on_impl_thread_->SetVisible(layer_tree_host_impl_->visible());
@@ skipping 316 matching lines @@
 bool SingleThreadProxy::IsInsideDraw() { return inside_draw_; }
 
 void SingleThreadProxy::DidActivateSyncTree() {
   // Non-impl-side painting finishes commit in DoCommit.  Impl-side painting
   // defers until here to simulate SetNextCommitWaitsForActivation.
   if (layer_tree_host_impl_->settings().impl_side_painting) {
     // This is required because NotifyReadyToActivate gets called when
     // the pending tree is not actually ready in the SingleThreadProxy.
     layer_tree_host_impl_->SetRequiresHighResToDraw();
 
-    // Synchronously call to CommitComplete. Resetting
-    // |commit_blocking_task_runner| would make sure all tasks posted during
-    // commit/activation before CommitComplete.
-    CommitComplete();
+    // Since activation could cause tasks to run, post CommitComplete
+    // separately so that it runs after these tasks.  This is the loose
+    // equivalent of blocking commit until activation and also running
+    // all tasks posted during commit/activation before CommitComplete.
+    MainThreadTaskRunner()->PostTask(
+        FROM_HERE, base::Bind(&SingleThreadProxy::CommitComplete,
+                              weak_factory_.GetWeakPtr()));
   }
 
   timing_history_.DidActivateSyncTree();
 }
 
 void SingleThreadProxy::DidManageTiles() {
   DCHECK(layer_tree_host_impl_->settings().impl_side_painting);
   DCHECK(Proxy::IsImplThread());
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->DidManageTiles();
@@ skipping 349 matching lines @@
 
 void SingleThreadProxy::DidBeginImplFrameDeadline() {
   layer_tree_host_impl_->ResetCurrentBeginFrameArgsForNextFrame();
 }
 
 void SingleThreadProxy::SendBeginFramesToChildren(const BeginFrameArgs& args) {
   layer_tree_host_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc