Refactor the way singleton-style resources are exposed via PPB_Instance

ppapi/shared_impl/api_id.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PPAPI_SHARED_IMPL_API_ID_H_
 #define PPAPI_SHARED_IMPL_API_ID_H_
 
 namespace ppapi {
 
 // These numbers must be all small integers. They are used in a lookup table
@@ skipping 57 matching lines @@
   API_ID_PPP_TEXT_INPUT,
   API_ID_PPP_VIDEO_CAPTURE_DEV,
   API_ID_PPP_VIDEO_DECODER_DEV,
 
   API_ID_RESOURCE_CREATION,
 
   // Must be last to indicate the number of interface IDs.
   API_ID_COUNT
 };
 
+// These IDs are used to access singleton resource objects using
+// PPB_Instance_API.GetSingletonResource.
+enum SingletonResourceID {
+  FLASH_SINGLETON_ID,
+  FLASH_CLIPBOARD_SINGLETON_ID,
+  GAMEPAD_SINGLETON_ID,
+};
+
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_API_ID_H_