Declare a new name for CompositingSurface completion callback.

content/browser/renderer_host/render_widget_host_view_base.h

Index: content/browser/renderer_host/render_widget_host_view_base.h
diff --git a/content/browser/renderer_host/render_widget_host_view_base.h b/content/browser/renderer_host/render_widget_host_view_base.h
index 4da2b56416d704d6dba154a4c15ad07922ce3ea0..ad81506b72fa5a595954417d099892a58c2a0498 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.h
+++ b/content/browser/renderer_host/render_widget_host_view_base.h
@@ -59,6 +59,12 @@ struct DidOverscrollParams;
 struct NativeWebKeyboardEvent;
 struct WebPluginGeometry;
 
+// TODO(Sikugu): Though we have the return status of the result here,
+// we should add the reason for failure as a new parameter to handle cases
+// efficiently.
+typedef const base::Callback<void(bool, const SkBitmap&)>
+    CopyFromCompositingSurfaceCallback;
+
 // Basic implementation shared by concrete RenderWidgetHostView subclasses.
 class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
                                                 public IPC::Listener {
@@ -258,7 +264,7 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
   virtual void CopyFromCompositingSurface(
       const gfx::Rect& src_subrect,
       const gfx::Size& dst_size,
-      const base::Callback<void(bool, const SkBitmap&)>& callback,
+      CopyFromCompositingSurfaceCallback& callback,
       const SkColorType color_type) = 0;
 
   // Copies the contents of the compositing surface, populating the given