Fix blits from multisampled renderbuffers to alpha:false WebGL back buffer.

ui/gl/gl_image.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 UI_GL_GL_IMAGE_H_
 #define UI_GL_GL_IMAGE_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 25 matching lines @@
   // Get the size of the image.
   virtual gfx::Size GetSize() = 0;
 
   // Get the internal format of the image.
   virtual unsigned GetInternalFormat() = 0;
 
   // Bind image to texture currently bound to |target|. Returns true on success.
   // It is valid for an implementation to always return false.
   virtual bool BindTexImage(unsigned target) = 0;
 
+  // Bind image to texture currently bound to |target|, forcing the texture's
+  // internal format to the specified one. This is a feature not available on
+  // all platforms. Returns true on success.  It is valid for an implementation
+  // to always return false.
+  virtual bool BindTexImageWithInternalformat(unsigned target,
+                                              unsigned internalformat);
+
   // Release image from texture currently bound to |target|.
   virtual void ReleaseTexImage(unsigned target) = 0;
 
   // Define texture currently bound to |target| by copying image into it.
   // Returns true on success. It is valid for an implementation to always
   // return false.
   virtual bool CopyTexImage(unsigned target) = 0;
 
   // Copy |rect| of image to |offset| in texture currently bound to |target|.
   // Returns true on success. It is valid for an implementation to always
@@ skipping 38 matching lines @@
 
  private:
   friend class base::RefCounted<GLImage>;
 
   DISALLOW_COPY_AND_ASSIGN(GLImage);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_IMAGE_H_