Disable overlay scrollbars in Blink when hidden by the compositor.

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_common.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 166 matching lines @@
   proto->set_layer_id(layer_id);
   Vector2dToProto(scroll_delta, proto->mutable_scroll_delta());
 }
 
 void LayerTreeHostCommon::ScrollUpdateInfo::FromProtobuf(
     const proto::ScrollUpdateInfo& proto) {
   layer_id = proto.layer_id();
   scroll_delta = ProtoToVector2d(proto.scroll_delta());
 }
 
+LayerTreeHostCommon::ScrollbarsUpdateInfo::ScrollbarsUpdateInfo()
+    : layer_id(Layer::INVALID_ID), hidden(true) {}
+
+LayerTreeHostCommon::ScrollbarsUpdateInfo::ScrollbarsUpdateInfo(int layer_id,
+                                                                bool hidden)
+    : layer_id(layer_id), hidden(hidden) {}
+
+bool LayerTreeHostCommon::ScrollbarsUpdateInfo::operator==(
+    const LayerTreeHostCommon::ScrollbarsUpdateInfo& other) const {
+  return layer_id == other.layer_id && hidden == other.hidden;
+}
+
+void LayerTreeHostCommon::ScrollbarsUpdateInfo::ToProtobuf(
+    proto::ScrollbarsUpdateInfo* proto) const {
+  proto->set_layer_id(layer_id);
+  proto->set_hidden(hidden);
+}
+
+void LayerTreeHostCommon::ScrollbarsUpdateInfo::FromProtobuf(
+    const proto::ScrollbarsUpdateInfo& proto) {
+  layer_id = proto.layer_id();
+  hidden = proto.hidden();
+}
+
 ScrollAndScaleSet::ScrollAndScaleSet()
     : page_scale_delta(1.f), top_controls_delta(0.f) {
 }
 
 ScrollAndScaleSet::~ScrollAndScaleSet() {}
 
 bool ScrollAndScaleSet::EqualsForTesting(const ScrollAndScaleSet& other) const {
   return scrolls == other.scrolls &&
          page_scale_delta == other.page_scale_delta &&
          elastic_overscroll_delta == other.elastic_overscroll_delta &&
@@ skipping 509 matching lines @@
 
 PropertyTrees* GetPropertyTrees(Layer* layer) {
   return layer->GetLayerTree()->property_trees();
 }
 
 PropertyTrees* GetPropertyTrees(LayerImpl* layer) {
   return layer->layer_tree_impl()->property_trees();
 }
 
 }  // namespace cc