Make SingleThreadProxy a SchedulerClient

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index b18b93a63518f976b00ff36c570f4b5ae57c7346..9fa3ecee5d6b5720a7b2637ecd8879cbfd516b78 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -25,6 +25,7 @@
 #include "cc/trees/blocking_task_runner.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
+#include "cc/trees/scoped_swap_promise_checker.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "ui/gfx/frame_time.h"
 
@@ -37,19 +38,6 @@ const double kSmoothnessTakesPriorityExpirationDelay = 0.25;
 
 unsigned int nextBeginFrameId = 0;
 
-class SwapPromiseChecker {
- public:
-  explicit SwapPromiseChecker(LayerTreeHost* layer_tree_host)
-      : layer_tree_host_(layer_tree_host) {}
-
-  ~SwapPromiseChecker() {
-    layer_tree_host_->BreakSwapPromises(SwapPromise::COMMIT_FAILS);
-  }
-
- private:
-  LayerTreeHost* layer_tree_host_;
-};
-
 }  // namespace
 
 struct ThreadProxy::CommitPendingRequest {
@@ -466,9 +454,10 @@ void ThreadProxy::SetNextCommitWaitsForActivation() {
 
 void ThreadProxy::SetDeferCommits(bool defer_commits) {
   DCHECK(IsMainThread());
-  DCHECK_NE(main().defer_commits, defer_commits);
-  main().defer_commits = defer_commits;
+  if (main().defer_commits == defer_commits)
+    return;
 
+  main().defer_commits = defer_commits;
   if (main().defer_commits)
     TRACE_EVENT_ASYNC_BEGIN0("cc", "ThreadProxy::SetDeferCommits", this);
   else
@@ -748,9 +737,9 @@ void ThreadProxy::BeginMainFrame(
   }
 
   // If the commit finishes, LayerTreeHost will transfer its swap promises to
-  // LayerTreeImpl. The destructor of SwapPromiseChecker checks LayerTressHost's
-  // swap promises.
-  SwapPromiseChecker swap_promise_checker(layer_tree_host());
+  // LayerTreeImpl. The destructor of ScopedSwapPromiseChecker aborts the
+  // remaining swap promises.
+  ScopedSwapPromiseChecker swap_promise_checker(layer_tree_host());
 
   main().commit_requested = false;
   main().commit_request_sent_to_impl_thread = false;