ServiceWorker: Make a way to retrieve a service worker version id (Blink)

Source/core/loader/FrameLoaderClient.h

Index: Source/core/loader/FrameLoaderClient.h
diff --git a/Source/core/loader/FrameLoaderClient.h b/Source/core/loader/FrameLoaderClient.h
index 32f0be2b51de445dd6d3463289c68982d4e2f43e..babd6d7d9d6470a0104968c7166edf4b7372686e 100644
--- a/Source/core/loader/FrameLoaderClient.h
+++ b/Source/core/loader/FrameLoaderClient.h
@@ -213,6 +213,8 @@ namespace blink {
 
         virtual bool isControlledByServiceWorker(DocumentLoader&) = 0;
 
+        virtual int64_t serviceWorkerID(DocumentLoader&) = 0;
+
         virtual SharedWorkerRepositoryClient* sharedWorkerRepositoryClient() { return 0; }
 
         virtual PassOwnPtr<blink::WebApplicationCacheHost> createApplicationCacheHost(blink::WebApplicationCacheHostClient*) = 0;