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

Source/modules/fetch/FetchHeaderList.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/fetch/FetchHeaderList.h"
 
 #include "core/fetch/FetchUtils.h"
+#include "core/frame/UseCounter.h"
 #include "platform/network/HTTPParsers.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 FetchHeaderList* FetchHeaderList::create()
 {
     return new FetchHeaderList();
 }
 
@@ skipping 127 matching lines @@
 {
     // "A name is a case-insensitive byte sequence that matches the field-name
     // token production."
     return isValidHTTPToken(name);
 }
 
 bool FetchHeaderList::isValidHeaderValue(const String& value)
 {
     // "A value is a byte sequence that matches the field-value token production
     // and contains no 0x0A or 0x0D bytes."
+
+    // Show deprecation warnings and count occurrences of such deprecated header values
+    if (!isValidHTTPFieldContentRFC7230(value) && isValidHTTPHeaderValue(value))
+        UseCounter::deprecationMessage(UseCounter::HeaderValueNotMatchingRFC7230);
+
     return isValidHTTPHeaderValue(value);
 }
 
 } // namespace blink