Push API: rename registration to subscription.

public/platform/WebPushProvider.h

Index: public/platform/WebPushProvider.h
diff --git a/public/platform/WebPushProvider.h b/public/platform/WebPushProvider.h
index af5d353ca5dd451d46d832c0eb8b02074d23df42..a525bee1204c4368ae9973852d4126626ffcc611 100644
--- a/public/platform/WebPushProvider.h
+++ b/public/platform/WebPushProvider.h
@@ -13,11 +13,15 @@ namespace blink {
 
 class WebServiceWorkerRegistration;
 struct WebPushError;
-struct WebPushRegistration;
-
-typedef WebCallbacks<WebPushRegistration, WebPushError> WebPushRegistrationCallbacks;
-typedef WebCallbacks<WebPushPermissionStatus, void> WebPushPermissionStatusCallbacks;
-typedef WebCallbacks<bool, WebPushError> WebPushUnregisterCallbacks;
+struct WebPushSubscription;
+
+using WebPushSubscriptionCallbacks = WebCallbacks<WebPushSubscription, WebPushError>;
+// FIXME: Remove when no longer used by the embedder - https://crbug.com/446883.
+using WebPushRegistrationCallbacks = WebPushSubscriptionCallbacks;
+using WebPushPermissionStatusCallbacks = WebCallbacks<WebPushPermissionStatus, void>;
+using WebPushUnsubscribeCallbacks = WebCallbacks<bool, WebPushError>;
+// FIXME: Remove when no longer used by the embedder - https://crbug.com/446883.
+using WebPushUnregisterCallbacks = WebPushUnsubscribeCallbacks;
 
 class WebPushProvider {
 public: