[M44] Revise deprecation warning for Client.postMessage.

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 380aea184e16ea3b13435acc80c4a5cbef5b08ac..1c8e52f49e4f83b35432f392ef9fb08eb93c0567 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -884,7 +884,7 @@ String UseCounter::deprecationMessage(Feature feature)
         return "'SVGSVGElement.unsuspendRedrawAll()' is deprecated, please do not use it. It is a no-op, as per SVG2 (https://svgwg.org/svg2-draft/struct.html#__svg__SVGSVGElement__unsuspendRedrawAll).";
 
     case ServiceWorkerClientPostMessage:
-        return "'Client.postMessage()' is an experimental API and may change. See https://github.com/slightlyoff/ServiceWorker/issues/609.";
+        return "'Client.postMessage()' will change to fire an event on 'navigator.serviceWorker' instead of 'window' in M45 (see: https://www.chromestatus.com/feature/5163630974730240).";
 
     case AttrChildAccess:
     case AttrChildChange: