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

plugin/idl/client.idl

 /*
  * 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 457 matching lines @@
     time or if you call ClearErrorCallback.
   %]
   void ClearErrorCallback();
 
   %[
     Makes all parameters get re-evaluated.
   %]
   void InvalidateAllParameters();
 
   %[
-    This function is only available in the test version of the plugin.
-    \param file_name Name to save screenshot to.
-    \return True on success.
+    Gets a copy of the current backbuffer of O3D as a data: url.
+
+    NOTE: Calling it will cause a render to happen.
+
+    \return A Data URL for the backbuffer.
   %]
-  bool SaveScreen(String file_name);
+  String ToDataURL();
+
+  %[
+    Gets a copy of the current backbuffer of O3D as a data: url.
+    \param mime_type The type of data url you want. Currently O3D only supports
+       image/png. See HTML5 canvas tag for info about toDataURL.
+    \return A Data URL for the backbuffer.
+  %]
+  [userglue] String ToDataURL(String mime_type);
 
   %[
     Returns the status of initializing the renderer so we can display the
     appropriate message. We require a certain minimum set of graphics
     capabilities. If the user's computer does not have his minimum
     set this will be GPU_NOT_UP_TO_SPEC. If the user is out of graphics
     resources this will be OUT_OF_RESOURCES. If some other error happened this
     will be INITIALIZATION_ERROR. Otherwise it will be SUCCESS.
   %]
   [userglue_getter, getter, plugin_data]
@@ skipping 74 matching lines @@
           plugin->service_locator()->GetService<o3d::ClientInfoManager>();
       return client_info_manager->client_info();
     }
     std::vector<o3d::DisplayMode> userglue_method_GetDisplayModes(
         void *plugin_data, o3d::Client *self) {
       std::vector<o3d::DisplayMode> modes;
       static_cast<glue::_o3d::PluginObject*>(plugin_data)->GetDisplayModes(
           &modes);
       return modes;
     }
+    o3d::String userglue_method_ToDataURL(o3d::Client* self,
+                                          const o3d::String& mime_type) {
+        // We ignore the mime_type since it's only a suggestion
+        // and we only return the required image/png type.
+        return self->ToDataURL();
+    }
     void userglue_method_SetFullscreenClickRegion(
         void *plugin_data, o3d::Client *self, int x, int y, int width,
         int height, int mode_id) {
       glue::_o3d::PluginObject *plugin =
           static_cast<glue::_o3d::PluginObject*>(plugin_data);
       if (!plugin->SetFullscreenClickRegion(x, y, width, height, mode_id)) {
         O3D_ERROR(plugin->service_locator())
             << "Call to SetFullscreenClickRegion failed.";
       }
     }
@@ skipping 40 matching lines @@
     o3d::Renderer::InitStatus userglue_getter_renderer_init_status(
         void* plugin_data, o3d::Client*) {
       return static_cast<glue::_o3d::PluginObject*>(
           plugin_data)->renderer_init_status();
     }
   %}
 };
 
 
 }  // namespace o3d