Show a warning when using sync xhr.

Source/core/frame/UseCounter.cpp

 
 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 789 matching lines @@
 
     case XHRProgressEventTotalSize:
         return "The XMLHttpRequest progress event property 'totalSize' is deprecated. Please use 'total' instead.";
 
     case ConsoleTimeline:
         return "console.timeline is deprecated. Please use the console.time instead.";
 
     case ConsoleTimelineEnd:
         return "console.timelineEnd is deprecated. Please use the console.timeEnd instead.";
 
+    case XMLHttpRequestSynchronousInNonWorkerOutsideBeforeUnload:
+        return "Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }
 }
 
 void UseCounter::count(CSSParserContext context, CSSPropertyID feature)
 {
     ASSERT(feature >= firstCSSProperty);
     ASSERT(feature <= lastCSSProperty);
@@ skipping 28 matching lines @@
 UseCounter* UseCounter::getFrom(const StyleSheetContents* sheetContents)
 {
     // FIXME: We may want to handle stylesheets that have multiple owners
     //        http://crbug.com/242125
     if (sheetContents && sheetContents->hasSingleOwnerNode())
         return getFrom(sheetContents->singleOwnerDocument());
     return 0;
 }
 
 } // namespace blink