Add support for runtime fall-back from o3d to o2d.

core/cross/renderer.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 809 matching lines @@
 
 bool Renderer::SafeToBindTexture(Texture* texture) const {
   if (current_render_surface_ &&
       current_render_surface_->texture() == texture) {
     return false;
   }
 
   return true;
 }
 
+// This is a factory function for creating 2D Renderer objects.  It only
+// functions in Cairo, in which case it is defined in the cairo platform
+// specific code.  This definition can be removed when all platforms

[Tristan Schmelcher 2, 2011/02/23 02:08:51]

I don't think you even need this now. It is not an error to declare a function
and never define it as long as there is no other code that references it. Since
the only call point is guarded by a SUPPORT_CAIRO, there shouldn't be any
problem with leaving it undefined.

+// build with Cairo.
+#if !defined(SUPPORT_CAIRO)
+Renderer* Renderer::Create2DRenderer(ServiceLocator* service_locator) {
+  return NULL;
+}
+#endif
+
 }  // namespace o3d