Deprecate the unofficial -webkit-transition media feature

Source/core/page/UseCounter.cpp

Index: Source/core/page/UseCounter.cpp
diff --git a/Source/core/page/UseCounter.cpp b/Source/core/page/UseCounter.cpp
index c6100facd047516cf858f5b544b81c7e7e618263..b64a8dcf5a94c16ab4ab49e7a0090b9386e34d01 100644
--- a/Source/core/page/UseCounter.cpp
+++ b/Source/core/page/UseCounter.cpp
@@ -148,6 +148,9 @@ String UseCounter::deprecationMessage(Feature feature)
     case DocumentClear:
         return "document.clear() is deprecated. This method doesn't do anything.";
 
+    case PrefixedTransitionMediaFeature:
+        return "The (-webkit-transition) media query feature is deprecated; please consider using (transition) instead.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();