Show deprecation warnings for header values in XHR according to RFC 7230

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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 953 matching lines @@
 
     case PrefixedPerformanceSetResourceTimingBufferSize:
         return replacedBy("Performance.webkitSetResourceTimingBufferSize", "Performance.setResourceTimingBufferSize");
 
     case PrefixedPerformanceResourceTimingBufferFull:
         return replacedBy("Performance.onwebkitresourcetimingbufferfull", "Performance.onresourcetimingbufferfull");
 
     case FetchAPIRequestContext:
         return "Request.context is deprecated and will be removed in M46 (see: https://www.chromestatus.com/feature/5534702526005248).";
 
+    case FetchHeaderValue:
+        return "isValidHTTPHeaderValue() will be deprecated and will be removed in future.";

[hiroshige, 2015/08/27 11:38:07]

How about "Header values not matching RFC 7230 will be deprecated (see:
https://www.chromestatus.com/feature/6457425448140800)"?
This message is for XHR/Fetch API users so should be a warning about header
values.
Also I created the chromestatus entry.

[shiva.jm, 2015/09/01 08:26:51]

Done.

+
     // 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 <= lastUnresolvedCSSProperty);
@@ skipping 27 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