Move overscroll bounce to impl thread

cc/input/input_handler.h

Index: cc/input/input_handler.h
diff --git a/cc/input/input_handler.h b/cc/input/input_handler.h
index b3205a8a6485bbe9839c7d621beb39ae15c83d31..d01098204df827b0ea9feae8c2d785e1d351f849 100644
--- a/cc/input/input_handler.h
+++ b/cc/input/input_handler.h
@@ -23,6 +23,7 @@ namespace ui { struct LatencyInfo; }
 namespace cc {
 
 class LayerScrollOffsetDelegate;
+class ScrollElasticityControllerClient;
 
 class CC_EXPORT InputHandlerClient {
  public:
@@ -140,6 +141,9 @@ class CC_EXPORT InputHandler {
   virtual scoped_ptr<SwapPromiseMonitor> CreateLatencyInfoSwapPromiseMonitor(
       ui::LatencyInfo* latency) = 0;
 
+  virtual ScrollElasticityControllerClient*
+      GetScrollElasticityControllerClient() = 0;
+
  protected:
   InputHandler() {}
   virtual ~InputHandler() {}