Replace CurrentPhysicalTimeTicks with a fallback in CurrentFrameTimeTicks.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 52c2c988bfbf781ae3e0b4fdf54943c225118fb3..10477dc2af297d281ab1eefeac22c6a87fe16893 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -388,11 +388,10 @@ class CC_EXPORT LayerTreeHostImpl
 
   void SetTreePriority(TreePriority priority);
 
+  void UpdateCurrentFrameTime();
   void ResetCurrentFrameTimeForNextFrame();
   virtual base::TimeTicks CurrentFrameTimeTicks();
 
-  virtual base::TimeTicks CurrentPhysicalTimeTicks() const;
-
   scoped_ptr<base::Value> AsValue() const { return AsValueWithFrame(NULL); }
   scoped_ptr<base::Value> AsValueWithFrame(FrameData* frame) const;
   scoped_ptr<base::Value> ActivationStateAsValue() const;
@@ -505,8 +504,6 @@ class CC_EXPORT LayerTreeHostImpl
   void AnimateScrollbarsRecursive(LayerImpl* layer,
                                   base::TimeTicks time);
 
-  void UpdateCurrentFrameTime(base::TimeTicks* ticks) const;
-
   LayerImpl* FindScrollLayerForDeviceViewportPoint(
       const gfx::PointF& device_viewport_point,
       InputHandler::ScrollInputType type,