Add more logging to cc scheduler to debug RAF frame loss.

cc/scheduler/scheduler_state_machine.h

 // 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.
 
 #ifndef CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_
 #define CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 219 matching lines @@
   bool PendingDrawsShouldBeAborted() const;
 
   bool SupportsProactiveBeginFrame() const;
 
   void SetContinuousPainting(bool continuous_painting) {
     continuous_painting_ = continuous_painting;
   }
 
   bool CouldSendBeginMainFrame() const;
 
+  // TODO(zmo): This is temporary for debugging crbug.com/393331.
+  // We should remove it afterwards.
+  std::string GetStatesForDebugging() const;
+
  protected:
   bool BeginFrameNeededToAnimateOrDraw() const;
   bool ProactiveBeginFrameWanted() const;
 
   // True if we need to force activations to make forward progress.
   bool PendingActivationsShouldBeForced() const;
 
   bool ShouldAnimate() const;
   bool ShouldBeginOutputSurfaceCreation() const;
   bool ShouldDrawForced() const;
@@ skipping 58 matching lines @@
   bool skip_begin_main_frame_to_reduce_latency_;
   bool continuous_painting_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_