Disable overlay scrollbars in Blink when hidden by the compositor.

cc/trees/layer_tree_host_common.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_COMMON_H_
 #define CC_TREES_LAYER_TREE_HOST_COMMON_H_
 
 #include <stddef.h>
 
 #include <limits>
@@ skipping 10 matching lines @@
 #include "cc/trees/layer_tree_impl.h"
 #include "cc/trees/property_tree.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
 namespace proto {
 class ScrollUpdateInfo;
+class ScrollbarsUpdateInfo;
 class ScrollAndScaleSet;
 }
 
 class LayerImpl;
 class Layer;
 class SwapPromise;
 class PropertyTrees;
 
 class CC_EXPORT LayerTreeHostCommon {
  public:
@@ skipping 94 matching lines @@
   static void CallFunctionForEveryLayer(LayerTree* layer,
                                         const Function& function);
 
   template <typename Function>
   static void CallFunctionForEveryLayer(LayerTreeImpl* layer,
                                         const Function& function);
 
   struct CC_EXPORT ScrollUpdateInfo {
     int layer_id;
     // TODO(miletus): Use ScrollOffset once LayerTreeHost/Blink fully supports
-    // franctional scroll offset.
+    // fractional scroll offset.
     gfx::Vector2d scroll_delta;
 
     ScrollUpdateInfo();
 
     bool operator==(const ScrollUpdateInfo& other) const;
 
     void ToProtobuf(proto::ScrollUpdateInfo* proto) const;
     void FromProtobuf(const proto::ScrollUpdateInfo& proto);
   };
+
+  struct CC_EXPORT ScrollbarsUpdateInfo {
+    int layer_id;
+    bool hidden;
+
+    ScrollbarsUpdateInfo();
+    ScrollbarsUpdateInfo(int layer_id, bool hidden);
+
+    bool operator==(const ScrollbarsUpdateInfo& other) const;
+
+    void ToProtobuf(proto::ScrollbarsUpdateInfo* proto) const;
+    void FromProtobuf(const proto::ScrollbarsUpdateInfo& proto);
+  };
 };
 
 struct CC_EXPORT ScrollAndScaleSet {
   ScrollAndScaleSet();
   ~ScrollAndScaleSet();
 
   // The inner viewport scroll delta is kept separate since it's special.
   // Because the inner (visual) viewport's maximum offset depends on the
   // current page scale, the two must be committed at the same time to prevent
   // clamping.
   LayerTreeHostCommon::ScrollUpdateInfo inner_viewport_scroll;
 
   std::vector<LayerTreeHostCommon::ScrollUpdateInfo> scrolls;
   float page_scale_delta;
   gfx::Vector2dF elastic_overscroll_delta;
   float top_controls_delta;
+  std::vector<LayerTreeHostCommon::ScrollbarsUpdateInfo> scrollbars;
   std::vector<std::unique_ptr<SwapPromise>> swap_promises;
 
   bool EqualsForTesting(const ScrollAndScaleSet& other) const;
   void ToProtobuf(proto::ScrollAndScaleSet* proto) const;
   void FromProtobuf(const proto::ScrollAndScaleSet& proto);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScrollAndScaleSet);
 };
 
@@ skipping 17 matching lines @@
     function(tree_impl->LayerById(id));
   }
 }
 
 CC_EXPORT PropertyTrees* GetPropertyTrees(Layer* layer);
 CC_EXPORT PropertyTrees* GetPropertyTrees(LayerImpl* layer);
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_COMMON_H_