Merge 162300 "Make second argument to CSSStyleSheet.insertRule() optional again"

Source/core/page/UseCounter.cpp

Index: Source/core/page/UseCounter.cpp
===================================================================
--- Source/core/page/UseCounter.cpp	(revision 162716)
+++ Source/core/page/UseCounter.cpp	(working copy)
@@ -682,6 +682,9 @@
     case ShowModalDialog:
         return "Chromium is considering deprecating showModalDialog. Please use window.open and postMessage instead.";
 
+    case CSSStyleSheetInsertRuleOptionalArg:
+        return "Calling CSSStyleSheet.insertRule() with one argument is deprecated. Please pass the index argument as well: insertRule(x, 0).";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();