Deprecate window.postMessage(m, transferables, origin) overload.

third_party/WebKit/Source/core/frame/Deprecation.cpp

Index: third_party/WebKit/Source/core/frame/Deprecation.cpp
diff --git a/third_party/WebKit/Source/core/frame/Deprecation.cpp b/third_party/WebKit/Source/core/frame/Deprecation.cpp
index 2f9514b77d54f65414fcfaff0ce395b375d33d93..2d0af914da0bfa524b8382c82ca03db8bb3a67d8 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -364,6 +364,9 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature)
     case UseCounter::WebAnimationsEasingAsFunctionLinear:
         return String::format("Specifying animation easing as a function is deprecated and all support will be removed in %s, at which point this will throw a TypeError. This warning may have been triggered by the Web Animations or Polymer polyfills. See http://crbug.com/601672 for details.", milestoneString(54));
 
+    case UseCounter::WindowPostMessageWithLegacyTargetOriginArgument:
+        return replacedWillBeRemoved("'window.postMessage(message, transferables, targetOrigin)'", "'window.postMessage(message, targetOrigin, transferables)'", 54, "5719033043222528");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();