Move scroll event handlers from layer to layer tree view.

cc/trees/layer_tree_impl.h

Index: cc/trees/layer_tree_impl.h
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index ffb93bd9aa08ea73e23945a87c09a28957090c1d..7f4c89c955967d44b6fd827c856fc5345587e69a 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -436,6 +436,13 @@ class CC_EXPORT LayerTreeImpl {
                                       const gfx::BoxF& box,
                                       gfx::BoxF* bounds) const;
 
+  bool have_scroll_event_handlers() const {
+    return have_scroll_event_handlers_;
+  }
+  void set_have_scroll_event_handlers(bool have_event_handlers) {
+    have_scroll_event_handlers_ = have_event_handlers;
+  }
+
   bool have_wheel_event_handlers() const { return have_wheel_event_handlers_; }
   void set_have_wheel_event_handlers(bool have_event_handlers) {
     have_wheel_event_handlers_ = have_event_handlers;
@@ -528,6 +535,7 @@ class CC_EXPORT LayerTreeImpl {
 
   int render_surface_layer_list_id_;
 
+  bool have_scroll_event_handlers_;
   bool have_wheel_event_handlers_;
 
   // Whether or not Blink's viewport size was shrunk by the height of the top