Remove support for PushSubscription.subscriptionId.

public/platform/modules/push_messaging/WebPushSubscription.h

Index: public/platform/modules/push_messaging/WebPushSubscription.h
diff --git a/public/platform/modules/push_messaging/WebPushSubscription.h b/public/platform/modules/push_messaging/WebPushSubscription.h
index 0c4f4efdb788dbc219dce3a146a1ce167e859365..9e4b1392a2e110e4abce7e728542d77d875d6405 100644
--- a/public/platform/modules/push_messaging/WebPushSubscription.h
+++ b/public/platform/modules/push_messaging/WebPushSubscription.h
@@ -5,19 +5,21 @@
 #ifndef WebPushSubscription_h
 #define WebPushSubscription_h
 
+#include "public/platform/WebCommon.h"
 #include "public/platform/WebString.h"
 
 namespace blink {
 
 struct WebPushSubscription {
-    WebPushSubscription(const WebString& endpoint, const WebString& subscriptionId)
+    explicit WebPushSubscription(const WebString& endpoint)
         : endpoint(endpoint)
-        , subscriptionId(subscriptionId)
     {
     }
 
+    // TODO(peter): Remove this constructor when the embedder switched over to the one above.
+    BLINK_PLATFORM_EXPORT WebPushSubscription(const WebString& endpointWithoutSubscriptionId, const WebString& subscriptionId);
+
     WebString endpoint;
-    WebString subscriptionId;
 };
 
 } // namespace blink