Scale scrollbar in use-zoom-for-dsf mode

cc/trees/layer_tree_host.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_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 230 matching lines @@
                                float scale,
                                base::TimeDelta duration);
 
   void ApplyScrollAndScale(ScrollAndScaleSet* info);
   void SetImplTransform(const gfx::Transform& transform);
 
   void SetDeviceScaleFactor(float device_scale_factor);
   void SetPaintedDeviceScaleFactor(float painted_device_scale_factor);
 
   float device_scale_factor() const { return device_scale_factor_; }
+  float painted_device_scale_factor() const {
+    return painted_device_scale_factor_;
+  }
 
   void UpdateTopControlsState(TopControlsState constraints,
                               TopControlsState current,
                               bool animate);
 
   HeadsUpDisplayLayer* hud_layer() const { return hud_layer_.get(); }
 
   Proxy* proxy() const { return proxy_.get(); }
   TaskRunnerProvider* task_runner_provider() const {
     return task_runner_provider_.get();
@@ skipping 259 matching lines @@
 
   uint32_t surface_id_namespace_;
   uint32_t next_surface_sequence_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_