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

core/cross/gl/renderer_gl.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 126 matching lines @@
 
   // Creates and returns a GL specific Sampler object.
   virtual Sampler::Ref CreateSampler();
 
   // Creates and returns a platform-specific RenderDepthStencilSurface object
   // for use as a depth-stencil render target.
   virtual RenderDepthStencilSurface::Ref CreateDepthStencilSurface(
       int width,
       int height);
 
-  // Saves a png screenshot 'file_name.png'.
-  // Returns true on success and false on failure.
-  virtual bool SaveScreen(const String& file_name);
+  // Overridden from Renderer.
+  virtual Bitmap::Ref TakeScreenshot();
 
   // Overridden from Renderer.
   virtual const int* GetRGBAUByteNSwizzleTable();
 
   // Makes this renderer active on the current thread if it is not active
   // already.
   void MakeCurrentLazy() {
     if (!IsCurrent()) MakeCurrent();
   }
 
@@ skipping 171 matching lines @@
   float polygon_offset_factor_;
   float polygon_offset_bias_;
 
   // Sets the stencils states for either front, back or both facing polys.
   void SetStencilStates(GLenum face, const StencilStates& stencil_states);
 };
 
 }  // namespace o3d
 
 #endif  // O3D_CORE_CROSS_GL_RENDERER_GL_H_