cc: Allow the main thread to cancel commits

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/output/context_provider.h"
 #include "cc/output/output_surface.h"
@@ skipping 153 matching lines @@
   DCHECK(Proxy::IsMainThread());
   DCHECK(!layer_tree_host_->output_surface_lost());
   return renderer_capabilities_for_main_thread_;
 }
 
 void SingleThreadProxy::SetNeedsAnimate() {
   // Thread-only feature.
   NOTREACHED();
 }
 
+void SingleThreadProxy::SetNeedsUpdateLayers() {
+  DCHECK(Proxy::IsMainThread());
+  layer_tree_host_->ScheduleComposite();
+}
+
 void SingleThreadProxy::DoCommit(scoped_ptr<ResourceUpdateQueue> queue) {
   DCHECK(Proxy::IsMainThread());
   // Commit immediately.
   {
     DebugScopedSetMainThreadBlocked mainThreadBlocked(this);
     DebugScopedSetImplThread impl(this);
 
     RenderingStatsInstrumentation* stats_instrumentation =
         layer_tree_host_->rendering_stats_instrumentation();
     base::TimeTicks start_time = stats_instrumentation->StartRecording();
@@ skipping 12 matching lines @@
             Proxy::MainThreadTaskRunner(),
             queue.Pass(),
             layer_tree_host_impl_->resource_provider());
     update_controller->Finalize();
 
     layer_tree_host_->FinishCommitOnImplThread(layer_tree_host_impl_.get());
 
     layer_tree_host_impl_->CommitComplete();
 
 #ifndef NDEBUG
-    // In the single-threaded case, the scroll deltas should never be
+    // In the single-threaded case, the scale and scroll deltas should never be
     // touched on the impl layer tree.
     scoped_ptr<ScrollAndScaleSet> scroll_info =
         layer_tree_host_impl_->ProcessScrollDeltas();
     DCHECK(!scroll_info->scrolls.size());
+    DCHECK_EQ(1.f, scroll_info->page_scale_delta);
 #endif
 
     base::TimeDelta duration = stats_instrumentation->EndRecording(start_time);
     stats_instrumentation->AddCommit(duration);
   }
   layer_tree_host_->CommitComplete();
   next_frame_is_newly_committed_frame_ = true;
 }
 
 void SingleThreadProxy::SetNeedsCommit() {
@@ skipping 259 matching lines @@
 void SingleThreadProxy::DidSwapFrame() {
   if (next_frame_is_newly_committed_frame_) {
     next_frame_is_newly_committed_frame_ = false;
     layer_tree_host_->DidCommitAndDrawFrame();
   }
 }
 
 bool SingleThreadProxy::CommitPendingForTesting() { return false; }
 
 }  // namespace cc