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

core/cross/gl/renderer_gl.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 1507 matching lines @@
 }
 
 const int* RendererGL::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 GL, we only ever return a GL renderer.
 Renderer* Renderer::CreateDefaultRenderer(ServiceLocator* service_locator) {
-#ifdef FORCE_CAIRO
-  return o2d::RendererCairo::CreateDefault(service_locator);
-#else
   return RendererGL::CreateDefault(service_locator);
-#endif
 }
 
 #ifdef OS_MACOSX
 void RendererGL::set_mac_cgl_context(CGLContextObj obj) {
   bool changed = (mac_cgl_context_ != obj);
   mac_cgl_context_ = obj;
   if (changed) {
     // We need to reset all of the OpenGL state when the context changes.
     alpha_function_ref_changed_ = true;
     alpha_blend_settings_changed_ = true;
@@ skipping 51 matching lines @@
 
   if (must_reset_context_) {
     // Apply the initial rendering states to the newly set context.
     SetInitialStates();
   }
 
   must_reset_context_ = false;
 }
 
 }  // namespace o3d