Update from https://crrev.com/316786

cc/layers/painted_scrollbar_layer.h

 // Copyright 2013 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_LAYERS_PAINTED_SCROLLBAR_LAYER_H_
 #define CC_LAYERS_PAINTED_SCROLLBAR_LAYER_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/input/scrollbar.h"
-#include "cc/layers/contents_scaling_layer.h"
+#include "cc/layers/layer.h"
 #include "cc/layers/scrollbar_layer_interface.h"
 #include "cc/layers/scrollbar_theme_painter.h"
 #include "cc/resources/layer_updater.h"
 #include "cc/resources/scoped_ui_resource.h"
 
 namespace cc {
 class ScrollbarThemeComposite;
 
 class CC_EXPORT PaintedScrollbarLayer : public ScrollbarLayerInterface,
-                                        public ContentsScalingLayer {
+                                        public Layer {
  public:
   scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
 
   static scoped_refptr<PaintedScrollbarLayer> Create(
       scoped_ptr<Scrollbar> scrollbar,
       int scroll_layer_id);
 
   bool OpacityCanAnimateOnImplThread() const override;
   ScrollbarLayerInterface* ToScrollbarLayer() override;
 
   // ScrollbarLayerInterface
   int ScrollLayerId() const override;
   void SetScrollLayer(int layer_id) override;
   void SetClipLayer(int layer_id) override;
 
   ScrollbarOrientation orientation() const override;
 
   // Layer interface
   bool Update(ResourceUpdateQueue* queue,
               const OcclusionTracker<Layer>* occlusion) override;
   void SetLayerTreeHost(LayerTreeHost* host) override;
   void PushPropertiesTo(LayerImpl* layer) override;
   void PushScrollClipPropertiesTo(LayerImpl* layer) override;
-  void CalculateContentsScale(float ideal_contents_scale,
-                              float* contents_scale_x,
-                              float* contents_scale_y,
-                              gfx::Size* content_bounds) override;
+
+  const gfx::Size& internal_content_bounds() const {
+    return internal_content_bounds_;
+  }
 
  protected:
   PaintedScrollbarLayer(scoped_ptr<Scrollbar> scrollbar, int scroll_layer_id);
   ~PaintedScrollbarLayer() override;
 
   // For unit tests
   UIResourceId track_resource_id() {
     return track_resource_.get() ? track_resource_->id() : 0;
   }
   UIResourceId thumb_resource_id() {
     return thumb_resource_.get() ? thumb_resource_->id() : 0;
   }
+  void UpdateInternalContentScale();
   void UpdateThumbAndTrackGeometry();
 
  private:
   gfx::Rect ScrollbarLayerRectToContentRect(const gfx::Rect& layer_rect) const;
   gfx::Rect OriginThumbRect() const;
 
-  template<typename T> void UpdateProperty(T value, T* prop) {
+  template <typename T>
+  bool UpdateProperty(T value, T* prop) {
     if (*prop == value)
-      return;
+      return false;
     *prop = value;
     SetNeedsPushProperties();
+    return true;
   }
 
   int MaxTextureSize();
   float ClampScaleToMaxTextureSize(float scale);
 
   UIResourceBitmap RasterizeScrollbarPart(const gfx::Rect& layer_rect,
                                           const gfx::Rect& content_rect,
                                           ScrollbarPart part);
 
   scoped_ptr<Scrollbar> scrollbar_;
   int scroll_layer_id_;
   int clip_layer_id_;
 
+  float internal_contents_scale_;
+  gfx::Size internal_content_bounds_;
+
   // Snapshot of properties taken in UpdateThumbAndTrackGeometry and used in
   // PushPropertiesTo.
   int thumb_thickness_;
   int thumb_length_;
   gfx::Point location_;
   gfx::Rect track_rect_;
   bool is_overlay_;
   bool has_thumb_;
 
   scoped_ptr<ScopedUIResource> track_resource_;
   scoped_ptr<ScopedUIResource> thumb_resource_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintedScrollbarLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PAINTED_SCROLLBAR_LAYER_H_