Merge the value of the push subscription id into the endpoint.

Source/core/frame/UseCounter.cpp

Index: Source/core/frame/UseCounter.cpp
diff --git a/Source/core/frame/UseCounter.cpp b/Source/core/frame/UseCounter.cpp
index 737af97e0aca74ab5ce71d5ca2c566920f2de4c6..5ac001855faadbc5070c0f86f0dfad02b9a1b630 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -912,6 +912,9 @@ String UseCounter::deprecationMessage(Feature feature)
     case FullscreenInsecureOrigin:
         return "requestFullscreen() will be deprecated over insecure origins in the future. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.";
 
+    case PushSubscriptionId:
+        return "'PushSubscription.subscriptionId' is deprecated and is now included in 'PushSubscription.endpoint'. It will be removed in Chrome 45, around August 2015.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();