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

Source/web/AssociatedURLLoader.cpp

Index: Source/web/AssociatedURLLoader.cpp
diff --git a/Source/web/AssociatedURLLoader.cpp b/Source/web/AssociatedURLLoader.cpp
index bd3345523abea6522eda68cd4b6a00f8e6f467cc..e576cf0d1a5665a95b7858a7a12b4fb84b61a329 100644
--- a/Source/web/AssociatedURLLoader.cpp
+++ b/Source/web/AssociatedURLLoader.cpp
@@ -33,6 +33,7 @@
 
 #include "core/fetch/CrossOriginAccessControl.h"
 #include "core/fetch/FetchUtils.h"
+#include "core/frame/UseCounter.h"
 #include "core/loader/DocumentThreadableLoader.h"
 #include "core/loader/DocumentThreadableLoaderClient.h"
 #include "platform/Timer.h"
@@ -69,6 +70,10 @@ private:
 
 void HTTPRequestHeaderValidator::visitHeader(const WebString& name, const WebString& value)
 {
+    // Show deprecation warnings and count occurrences of such deprecated header values
+    if (isValidHTTPHeaderValueForFetch(value))
+        UseCounter::deprecationMessage(UseCounter::FetchHeaderValue);

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

I think deprecation message here is not needed (or at least out of scope of this
CL).
Although isValidHTTPHeaderValue() is called, this is not directly coupled with
XHR or Fetch API.

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

Done.

+
     m_isSafe = m_isSafe && isValidHTTPToken(name) && !FetchUtils::isForbiddenHeaderName(name) && isValidHTTPHeaderValue(value);
 }