cc: Make separate interface for BeginFrame ipc from OutputSurface

cc/scheduler/begin_frame_source.cc

 // Copyright 2014 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/scheduler/begin_frame_source.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/logging.h"
@@ skipping 61 matching lines @@
   return needs_begin_frames_;
 }
 
 void BeginFrameSourceMixIn::SetNeedsBeginFrames(bool needs_begin_frames) {
   DEBUG_FRAMES("BeginFrameSourceMixIn::SetNeedsBeginFrames",
                "current state",
                needs_begin_frames_,
                "new state",
                needs_begin_frames);
   if (needs_begin_frames_ != needs_begin_frames) {
+    needs_begin_frames_ = needs_begin_frames;
     OnNeedsBeginFramesChange(needs_begin_frames);
   }
-  needs_begin_frames_ = needs_begin_frames;
 }
 
 void BeginFrameSourceMixIn::AddObserver(BeginFrameObserver* obs) {
   DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver",
                "current observer",
                observer_,
                "to add observer",
                obs);
   DCHECK(!observer_);
   observer_ = obs;
@@ skipping 388 matching lines @@
   if (!observer_->LastUsedBeginFrameArgs().IsValid())
     return true;
 
   // Only allow new args have a *strictly bigger* frame_time value and statisfy
   // minimum interval requirement.
   return (args.frame_time >=
           observer_->LastUsedBeginFrameArgs().frame_time + minimum_interval_);
 }
 
 }  // namespace cc