Add WebGraphicsContext support for readbacks from any framebuffer.

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.h

 // Copyright (c) 2011 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_RENDERER_GPU_WEBGRAPHICSCONTEXT3D_COMMAND_BUFFER_IMPL_H_
 #define CONTENT_RENDERER_GPU_WEBGRAPHICSCONTEXT3D_COMMAND_BUFFER_IMPL_H_
 #pragma once
 
 #if defined(ENABLE_GPU)
 
@@ skipping 51 matching lines @@
   virtual int width();
   virtual int height();
 
   virtual bool isGLES2Compliant();
 
   virtual bool setParentContext(WebGraphicsContext3D* parent_context);
 
   virtual void reshape(int width, int height);
 
   virtual bool readBackFramebuffer(unsigned char* pixels, size_t buffer_size);
+  virtual bool readBackFramebuffer(unsigned char* pixels, size_t buffer_size,
+                                   WebGLId framebuffer, int width, int height);
 
   virtual WebGLId getPlatformTextureId();
   virtual void prepareTexture();
 
   virtual void activeTexture(WGC3Denum texture);
   virtual void attachShader(WebGLId program, WebGLId shader);
   virtual void bindAttribLocation(WebGLId program, WGC3Duint index,
                                   const WGC3Dchar* name);
   virtual void bindBuffer(WGC3Denum target, WebGLId buffer);
   virtual void bindFramebuffer(WGC3Denum target, WebGLId framebuffer);
@@ skipping 380 matching lines @@
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   scoped_array<uint8> scanline_;
   void FlipVertically(uint8* framebuffer,
                       unsigned int width,
                       unsigned int height);
 #endif
 };
 
 #endif  // defined(ENABLE_GPU)
 #endif  // CONTENT_RENDERER_GPU_WEBGRAPHICSCONTEXT3D_COMMAND_BUFFER_IMPL_H_