Deprecate EventSource.URL and WebSocket.URL

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 4a55d519c4d1b462f8a5ef9e3083e78204740d06..bf71ea3f018a47bdaf8c808d7ca5ee3bcfbe2ba0 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -739,6 +739,12 @@ String UseCounter::deprecationMessage(Feature feature)
     case OpenWebDatabaseSyncInWorker:
         return "'openDatabaseSync' is deprecated. Please switch to Indexed Database API.";
 
+    case EventSourceURL:
+        return "'EventSource.URL' is deprecated. Please use 'EventSource.url' instead.";
+
+    case WebSocketURL:
+        return "'WebSocket.URL' is deprecated. Please use 'WebSocket.url' instead.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();