Maintain minimal error response.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 69fe661283393fdb0315cda39e74758e57cc291c..e4ea29d24b46cc0a4cd7653be208dedd471873d0 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -186,10 +186,11 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   gfx::Size GetRequestedRendererSize() const override;
   void SelectionBoundsChanged(
       const ViewHostMsg_SelectionBounds_Params& params) override;
-  void CopyFromCompositingSurface(const gfx::Rect& src_subrect,
-                                  const gfx::Size& dst_size,
-                                  ReadbackRequestCallback& callback,
-                                  const SkColorType color_type) override;
+  void CopyFromCompositingSurface(
+      const gfx::Rect& src_subrect,
+      const gfx::Size& dst_size,
+      ReadbackRequestCallback& callback,
+      const SkColorType preferred_color_type) override;
   void CopyFromCompositingSurfaceToVideoFrame(
       const gfx::Rect& src_subrect,
       const scoped_refptr<media::VideoFrame>& target,
@@ -358,7 +359,7 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
 
   // Exposed for tests.
   aura::Window* window() { return window_; }
-  SkColorType PreferredReadbackFormat() override;
+
   DelegatedFrameHost* GetDelegatedFrameHost() const {
     return delegated_frame_host_.get();
   }