Refactor the way singleton-style resources are exposed via PPB_Instance

ppapi/shared_impl/resource.h

Index: ppapi/shared_impl/resource.h
diff --git a/ppapi/shared_impl/resource.h b/ppapi/shared_impl/resource.h
index 3f1f5abb9626db320091e25fcc7f1f47024472c9..6100a8b01d14438d853b92911b536329a884410e 100644
--- a/ppapi/shared_impl/resource.h
+++ b/ppapi/shared_impl/resource.h
@@ -40,6 +40,7 @@
   F(PPB_Flash_Functions_API) \
   F(PPB_Flash_Menu_API) \
   F(PPB_Flash_MessageLoop_API) \
+  F(PPB_Gamepad_API) \
   F(PPB_Graphics2D_API) \
   F(PPB_Graphics3D_API) \
   F(PPB_HostResolver_Private_API) \
@@ -96,6 +97,14 @@ enum ResourceObjectType {
   OBJECT_IS_PROXY
 };
 
+// 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,
+};
+
 class PPAPI_SHARED_EXPORT Resource : public base::RefCounted<Resource> {
  public:
   // Constructor for impl and non-proxied, instance-only objects.