cc: Adding BeginFrameTracker object and removing Now() from LTHI.

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 03ddaa050d8288544f7fd87a59f981c484282061..6eee10b7652142565f444511a9a960c406f29e2a 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -32,6 +32,7 @@
 #include "cc/quads/render_pass.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/tile_manager.h"
+#include "cc/scheduler/begin_frame_tracker.h"
 #include "cc/scheduler/commit_earlyout_reason.h"
 #include "cc/scheduler/draw_result.h"
 #include "skia/ext/refptr.h"
@@ -432,14 +433,14 @@ class CC_EXPORT LayerTreeHostImpl
   void SetTreePriority(TreePriority priority);
   TreePriority GetTreePriority() const;
 
-  void UpdateCurrentBeginFrameArgs(const BeginFrameArgs& args);
+  // TODO(mithro): Remove these methods which expose control of the internal
+  // BeginFrameArgs to external callers. LayerTreeHostImpl should manage its
+  // own frame time based on WillBeginImplFrame and other methods.
   void ResetCurrentBeginFrameArgsForNextFrame();
   virtual BeginFrameArgs CurrentBeginFrameArgs() const;
 
   // Expected time between two begin impl frame calls.
-  base::TimeDelta begin_impl_frame_interval() const {
-    return begin_impl_frame_interval_;
-  }
+  base::TimeDelta CurrentBeginFrameInterval() const;
 
   void AsValueInto(base::debug::TracedValue* value) const;
   void AsValueWithFrameInto(FrameData* frame,
@@ -529,6 +530,8 @@ class CC_EXPORT LayerTreeHostImpl
   LayerTreeHostImplClient* client_;
   Proxy* proxy_;
 
+  BeginFrameTracker current_begin_frame_tracker_;
+
  private:
   void CreateAndSetRenderer();
   void CreateAndSetTileManager();
@@ -702,11 +705,6 @@ class CC_EXPORT LayerTreeHostImpl
 
   gfx::Rect viewport_damage_rect_;
 
-  BeginFrameArgs current_begin_frame_args_;
-
-  // Expected time between two begin impl frame calls.
-  base::TimeDelta begin_impl_frame_interval_;
-
   scoped_ptr<AnimationRegistrar> animation_registrar_;
 
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;