Move scroll event handlers from layer to layer tree view.

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index 0dfa3db6fa4540434b6056cfa818957f117e2ff4..24ae93291ebf13f2f225c3c6231e8f084b03b736 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -71,7 +71,6 @@ Layer::Layer(const LayerSettings& settings)
       main_thread_scrolling_reasons_(
           MainThreadScrollingReason::kNotScrollingOnMain),
       should_flatten_transform_from_property_tree_(false),
-      have_scroll_event_handlers_(false),
       user_scrollable_horizontal_(true),
       user_scrollable_vertical_(true),
       is_root_for_isolated_group_(false),
@@ -970,14 +969,6 @@ void Layer::ClearMainThreadScrollingReasons() {
   SetNeedsCommit();
 }
 
-void Layer::SetHaveScrollEventHandlers(bool have_scroll_event_handlers) {
-  DCHECK(IsPropertyChangeAllowed());
-  if (have_scroll_event_handlers_ == have_scroll_event_handlers)
-    return;
-  have_scroll_event_handlers_ = have_scroll_event_handlers;
-  SetNeedsCommit();
-}
-
 void Layer::SetNonFastScrollableRegion(const Region& region) {
   DCHECK(IsPropertyChangeAllowed());
   if (non_fast_scrollable_region_ == region)
@@ -1213,7 +1204,6 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
   layer->SetBackgroundFilters(background_filters());
   layer->SetMasksToBounds(masks_to_bounds_);
   layer->set_main_thread_scrolling_reasons(main_thread_scrolling_reasons_);
-  layer->SetHaveScrollEventHandlers(have_scroll_event_handlers_);
   layer->SetNonFastScrollableRegion(non_fast_scrollable_region_);
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
   layer->SetContentsOpaque(contents_opaque_);
@@ -1482,7 +1472,6 @@ void Layer::LayerSpecificPropertiesToProto(proto::LayerProperties* proto) {
 
   base->set_masks_to_bounds(masks_to_bounds_);
   base->set_main_thread_scrolling_reasons(main_thread_scrolling_reasons_);
-  base->set_have_scroll_event_handlers(have_scroll_event_handlers_);
   RegionToProto(non_fast_scrollable_region_,
                 base->mutable_non_fast_scrollable_region());
   RegionToProto(touch_event_handler_region_,
@@ -1567,7 +1556,6 @@ void Layer::FromLayerSpecificPropertiesProto(
   has_render_surface_ = base.has_render_surface();
   masks_to_bounds_ = base.masks_to_bounds();
   main_thread_scrolling_reasons_ = base.main_thread_scrolling_reasons();
-  have_scroll_event_handlers_ = base.have_scroll_event_handlers();
   non_fast_scrollable_region_ =
       RegionFromProto(base.non_fast_scrollable_region());
   touch_event_handler_region_ =