Query the preferred readback config in CopyFromBackingStore

content/common/gpu/client/gl_helper_readback_support.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 CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
 #define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_
 
 #include "content/common/gpu/client/gl_helper.h"
 
 namespace content {
 
 class CONTENT_EXPORT GLHelperReadbackSupport {
  public:
   GLHelperReadbackSupport(gpu::gles2::GLES2Interface* gl);
 
   ~GLHelperReadbackSupport();
 
   // Checks whether the readback (Color read format and type) is supported
   // for the requested texture format  by the hardware or not.
   // For ex: some hardwares have rgb565 readback
   // support when binded with the frame buffer for others it may fail.
   // Here we pass the internal textureformat as skia config.
   bool IsReadbackConfigSupported(SkBitmap::Config texture_format);
 
+  SkBitmap::Config PreferredReadbackFormat();
+
  private:
   enum FormatSupport { FORMAT_NOT_SUPPORTED = 0, FORMAT_SUPPORTED, };
 
   // This populates the format_support_table with the list of supported
   // formats.
   void InitializeReadbackSupport();
 
   // This api is called  once per format and it is done in the
   // InitializeReadbackSupport. We should not use this any where
   // except the InitializeReadbackSupport.Calling this at other places
   // can distrub the state of normal gl operations.
   void CheckForReadbackSupport(SkBitmap::Config texture_format);
 
   // Helper functions for checking the supported texture formats.
   // Avoid using this API in between texture operations, as this does some
   // teture opertions (bind, attach) internally.
   bool SupportsFormat(GLint format, GLint type);
 
   FormatSupport format_support_table_[SkBitmap::kConfigCount];
 
   gpu::gles2::GLES2Interface* gl_;
 
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_CLIENT_GL_HELPER_READBACK_SUPPORT_H_