Query the preferred readback config in CopyFromBackingStore

content/port/browser/render_widget_host_view_port.h

 // Copyright (c) 2012 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 CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_
 #define CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 308 matching lines @@
   // one depending on the current state.
   virtual void CreateBrowserAccessibilityManagerIfNeeded() = 0;
 
   // Return a value that is incremented each time the renderer swaps a new frame
   // to the view.
   virtual uint32 RendererFrameNumber() = 0;
   // Called each time the RenderWidgetHost receives a new frame for display from
   // the renderer.
   virtual void DidReceiveRendererFrame() = 0;
 
+  virtual SkBitmap::Config PreferredReadbackFormat() = 0;
+
 #if defined(OS_MACOSX)
   // Does any event handling necessary for plugin IME; should be called after
   // the plugin has already had a chance to process the event. If plugin IME is
   // not enabled, this is a no-op, so it is always safe to call.
   // Returns true if the event was handled by IME.
   virtual bool PostProcessEventForPluginIme(
       const NativeWebKeyboardEvent& event) = 0;
 #endif
 
 #if defined(OS_ANDROID)
   virtual void ShowDisambiguationPopup(const gfx::Rect& target_rect,
                                        const SkBitmap& zoomed_bitmap) = 0;
 #endif
 
 #if defined(OS_WIN)
   virtual void SetParentNativeViewAccessible(
       gfx::NativeViewAccessible accessible_parent) = 0;
 
   // Returns an HWND that's given as the parent window for windowless Flash to
   // workaround crbug.com/301548.
   virtual gfx::NativeViewId GetParentForWindowlessPlugin() const = 0;
 #endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_