Make SingleThreadProxy a SchedulerClient

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index af342998f42d2045c06498307853e535213bb774..fc841c2504dd920ae61ba56b6e9769d5ed521d9a 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -209,8 +209,8 @@ void Scheduler::SetupNextBeginImplFrameIfNeeded() {
 
 void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
   TRACE_EVENT0("cc", "Scheduler::BeginImplFrame");
-  DCHECK(state_machine_.begin_impl_frame_state() ==
-         SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
+  DCHECK_EQ(state_machine_.begin_impl_frame_state(),
+            SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(state_machine_.HasInitializedOutputSurface());
   last_begin_impl_frame_args_ = args;
   last_begin_impl_frame_args_.deadline -= client_->DrawDurationEstimate();