Add use counters for lots of DOM APIs.

third_party/WebKit/Source/core/events/MessageEvent.idl

Index: third_party/WebKit/Source/core/events/MessageEvent.idl
diff --git a/third_party/WebKit/Source/core/events/MessageEvent.idl b/third_party/WebKit/Source/core/events/MessageEvent.idl
index 5c3a7e34eb4316c3979851519ea456043f42c863..838b722c9541357651059514afe1555d9a56434d 100644
--- a/third_party/WebKit/Source/core/events/MessageEvent.idl
+++ b/third_party/WebKit/Source/core/events/MessageEvent.idl
@@ -36,10 +36,10 @@
     readonly attribute DOMString origin;
     readonly attribute DOMString lastEventId;
     // TODO(bashi): |source| should be (WindowProxy or MessagePort)?
-    readonly attribute EventTarget? source;
+    [Measure] readonly attribute EventTarget? source;
     // TODO(foolip): |ports| should be FrozenArray<MessagePort>?
-    readonly attribute MessagePort[]? ports;
-    [RuntimeEnabled=suborigins] readonly attribute DOMString suborigin;
+    [Measure] readonly attribute MessagePort[]? ports;
+    [Measure, RuntimeEnabled=suborigins] readonly attribute DOMString suborigin;
 
     // TODO(foolip): None of the initMessageEvent() arguments should be
     // optional, and |sourceArg| and |portsArg| are of the wrong type.