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

core/cross/command_buffer/renderer_cb.h

 /*
  * 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 123 matching lines @@
   // Creates and returns a platform specific Sampler object.
   virtual Sampler::Ref CreateSampler();
 
   // TODO: Fill this in
   virtual RenderDepthStencilSurface::Ref CreateDepthStencilSurface(
       int width,
       int height) {
     return RenderDepthStencilSurface::Ref();
   }
 
-  // Saves a png screenshot.
-  // Returns true on success and false on failure.
-  virtual bool SaveScreen(const String& file_name);
+  // Overridden from Renderer.
+  virtual Bitmap::Ref TakeScreenshot();
 
   // Gets the allocator for vertex buffer IDs.
   IdAllocator &vertex_buffer_ids() { return vertex_buffer_ids_; }
 
   // Gets the allocator for index buffer IDs.
   IdAllocator &index_buffer_ids() { return index_buffer_ids_; }
 
   // Gets the allocator for vertex struct IDs.
   IdAllocator &vertex_structs_ids() { return vertex_structs_ids_; }
 
@@ skipping 101 matching lines @@
 
   class StateManager;
   scoped_ptr<StateManager> state_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererCB);
 };
 
 }  // namespace o3d
 
 #endif  // O3D_CORE_CROSS_COMMAND_BUFFER_RENDERER_CB_H_