Feed ScrollableArea::showOverlayScrollbars into ScrollbarAnimationController.

cc/blink/web_layer_impl.h

 // Copyright 2014 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_BLINK_WEB_LAYER_IMPL_H_
 #define CC_BLINK_WEB_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 108 matching lines @@
       const override;
   void setScrollClient(blink::WebLayerScrollClient* client) override;
   void setLayerClient(cc::LayerClient* client) override;
   const cc::Layer* ccLayer() const override;
   cc::Layer* ccLayer() override;
   void setElementId(const cc::ElementId&) override;
   cc::ElementId elementId() const override;
   void setCompositorMutableProperties(uint32_t properties) override;
   uint32_t compositorMutableProperties() const override;
   void setHasWillChangeTransformHint(bool has_will_change) override;
+  void showScrollbars() override;
 
   void setScrollParent(blink::WebLayer* parent) override;
   void setClipParent(blink::WebLayer* parent) override;
 
  protected:
   scoped_refptr<cc::Layer> layer_;
 
   bool contents_opaque_is_fixed_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebLayerImpl);
 };
 
 }  // namespace cc_blink
 
 #endif  // CC_BLINK_WEB_LAYER_IMPL_H_