Fix CopyFromBackingStore giving back empty SkBitmaps on mac.

content/browser/renderer_host/compositing_iosurface_mac.mm

 // 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.
 
 #include "content/browser/renderer_host/compositing_iosurface_mac.h"
 
 #include <OpenGL/OpenGL.h>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 847 matching lines @@
   CHECK_GL_ERROR();
 
   if (buf) {
     SkAutoLockPixels bitmap_lock(copy_context_.out_buf);
     memcpy(copy_context_.out_buf.getPixels(), buf,
            copy_context_.dest_size.GetArea() * 4);
     glUnmapBufferARB(GL_PIXEL_PACK_BUFFER_ARB); CHECK_GL_ERROR();
   }
   glBindBufferARB(GL_PIXEL_PACK_BUFFER_ARB, 0); CHECK_GL_ERROR();
 
+  // Ref so they don't get deleted in CleanupResourcesForCopy.
   base::Callback<void(bool, const SkBitmap&)> callback = copy_context_.callback;
+  SkBitmap out_buf = copy_context_.out_buf;
+
   CleanupResourcesForCopy();
   CGLSetCurrentContext(0);
 
-  callback.Run(buf != NULL, copy_context_.out_buf);
+  callback.Run(buf != NULL, out_buf);
 }
 
 void CompositingIOSurfaceMac::CleanupResourcesForCopy() {
   if (!copy_context_.started)
     return;
 
   glDeleteFramebuffersEXT(1, &copy_context_.frame_buffer); CHECK_GL_ERROR();
   glDeleteTextures(1, &copy_context_.frame_buffer_texture); CHECK_GL_ERROR();
   glDeleteBuffers(1, &copy_context_.pixel_buffer); CHECK_GL_ERROR();
   if (copy_context_.use_fence) {
     glDeleteFencesAPPLE(1, &copy_context_.fence); CHECK_GL_ERROR();
   }
   copy_context_.Reset();
 }
 
 }  // namespace content