This CL adds client.toDataURL which gets the contents...

core/cross/command_buffer/renderer_cb.cc

 /*
  * Copyright 2009, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 350 matching lines @@
   command_buffer::CommandBufferEntry args[6];
   args[0].value_uint32 = left;
   args[1].value_uint32 = top;
   args[2].value_uint32 = width;
   args[3].value_uint32 = height;
   args[4].value_float = min_z;
   args[5].value_float = max_z;
   helper_->AddCommand(command_buffer::SET_VIEWPORT, 6, args);
 }
 
-bool RendererCB::SaveScreen(const String& file_name) {
-  // TODO
-  return false;
+Bitmap::Ref RendererCB::TakeScreenshot() {
+  return Bitmap::Ref();
 }
 
 const int* RendererCB::GetRGBAUByteNSwizzleTable() {
   static int swizzle_table[] = { 0, 1, 2, 3, };
   return swizzle_table;
 }
 
 // This is a factory function for creating Renderer objects.  Since
 // we're implementing command buffers, we only ever return a CB renderer.
 Renderer* Renderer::CreateDefaultRenderer(ServiceLocator* service_locator) {
   return RendererCB::CreateDefault(service_locator);
 }
 }  // namespace o3d