Adding support for VSyncProvider to the software drawing path

cc/output/software_output_device.h

 // Copyright 2012 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_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_
 #define CC_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_
 
 #include "base/basictypes.h"
 #include "cc/base/cc_export.h"
 #include "skia/ext/refptr.h"
 // TODO(robertphillips): change this to "class SkBaseDevice;"
 #include "third_party/skia/include/core/SkDevice.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 #include "ui/gfx/vector2d.h"
 
 class SkBitmap;
 class SkCanvas;
 
+namespace gfx {
+class VSyncProvider;
+}
+
 namespace cc {
 
 class SoftwareFrameData;
 
 // This is a "tear-off" class providing software drawing support to
 // OutputSurface, such as to a platform-provided window framebuffer.
 class CC_EXPORT SoftwareOutputDevice {
  public:
   SoftwareOutputDevice();
   virtual ~SoftwareOutputDevice();
@@ skipping 28 matching lines @@
 
   // Ensures that there is a backing buffer available on this instance.
   virtual void EnsureBackbuffer() {}
 
   // TODO(skaslev) Remove this after UberCompositor lands.
   // Called in response to receiving a SwapBuffersAck. At this point, software
   // frame identified by id can be reused or discarded as it is no longer being
   // displayed.
   virtual void ReclaimSoftwareFrame(unsigned id);
 
+  // VSyncProvider used to update the timer used to schedule draws with the
+  // hardware vsync. Return NULL if a provider doesn't exist.
+  virtual gfx::VSyncProvider* GetVSyncProvider();
+
  protected:
   gfx::Size viewport_size_;
   gfx::Rect damage_rect_;
   skia::RefPtr<SkBaseDevice> device_;
   skia::RefPtr<SkCanvas> canvas_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SoftwareOutputDevice);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_SOFTWARE_OUTPUT_DEVICE_H_