Move overscroll bounce to impl thread

content/renderer/input/input_handler_proxy.h

Index: content/renderer/input/input_handler_proxy.h
diff --git a/content/renderer/input/input_handler_proxy.h b/content/renderer/input/input_handler_proxy.h
index 35075513dfc90b6c95e15ed2187ffd6bf2156dbb..730a2a89cb22d4c55c937a81155dc7c97ff02265 100644
--- a/content/renderer/input/input_handler_proxy.h
+++ b/content/renderer/input/input_handler_proxy.h
@@ -18,6 +18,7 @@
 namespace content {
 
 class InputHandlerProxyClient;
+class InputScrollElasticityController;
 
 // This class is a proxy between the content input event filtering and the
 // compositor's input handling logic. InputHandlerProxy instances live entirely
@@ -121,6 +122,8 @@ class CONTENT_EXPORT InputHandlerProxy
 
   bool smooth_scroll_enabled_;
 
+  scoped_ptr<InputScrollElasticityController> scroll_elasticity_controller_;
+
   DISALLOW_COPY_AND_ASSIGN(InputHandlerProxy);
 };