Move have_wheel_event_handlers to WebLayerTreeView.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 881cff839349a24b63ff05b5715994f4eccaa472..529beaeb2c33f7a2ee4ee80e546599abce5ba91f 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -183,6 +183,7 @@ LayerTreeHost::LayerTreeHost(InitParams* params, CompositorMode mode)
       gpu_rasterization_histogram_recorded_(false),
       background_color_(SK_ColorWHITE),
       has_transparent_background_(false),
+      have_wheel_event_handlers_(false),
       did_complete_scale_animation_(false),
       in_paint_layer_contents_(false),
       id_(s_layer_tree_host_sequence_number.GetNext() + 1),
@@ -391,6 +392,7 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
 
   sync_tree->set_background_color(background_color_);
   sync_tree->set_has_transparent_background(has_transparent_background_);
+  sync_tree->set_have_wheel_event_handlers(have_wheel_event_handlers_);
 
   if (page_scale_layer_.get() && inner_viewport_scroll_layer_.get()) {
     sync_tree->SetViewportLayersFromIds(
@@ -1105,6 +1107,14 @@ void LayerTreeHost::RegisterSelection(const LayerSelection& selection) {
   SetNeedsCommit();
 }
 
+void LayerTreeHost::SetHaveWheelEventHandlers(bool have_event_handlers) {
+  if (have_wheel_event_handlers_ == have_event_handlers)
+    return;
+
+  have_wheel_event_handlers_ = have_event_handlers;
+  SetNeedsCommit();
+}
+
 int LayerTreeHost::ScheduleMicroBenchmark(
     const std::string& benchmark_name,
     scoped_ptr<base::Value> value,
@@ -1430,6 +1440,7 @@ void LayerTreeHost::ToProtobufForCommit(proto::LayerTreeHost* proto) const {
       content_is_suitable_for_gpu_rasterization_);
   proto->set_background_color(background_color_);
   proto->set_has_transparent_background(has_transparent_background_);
+  proto->set_have_wheel_event_handlers(have_wheel_event_handlers_);
   proto->set_in_paint_layer_contents(in_paint_layer_contents_);
   proto->set_id(id_);
   proto->set_next_commit_forces_redraw(next_commit_forces_redraw_);
@@ -1494,6 +1505,7 @@ void LayerTreeHost::FromProtobufForCommit(const proto::LayerTreeHost& proto) {
       proto.content_is_suitable_for_gpu_rasterization();
   background_color_ = proto.background_color();
   has_transparent_background_ = proto.has_transparent_background();
+  have_wheel_event_handlers_ = proto.have_wheel_event_handlers();
   in_paint_layer_contents_ = proto.in_paint_layer_contents();
   id_ = proto.id();
   next_commit_forces_redraw_ = proto.next_commit_forces_redraw();