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

Source/platform/network/HTTPParsers.cpp

 /*
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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:
@@ skipping 97 matching lines @@
 }
 
 bool isValidHTTPHeaderValue(const String& name)
 {
     // FIXME: This should really match name against
     // field-value in section 4.2 of RFC 2616.
 
     return name.containsOnlyLatin1() && !name.contains('\r') && !name.contains('\n') && !name.contains(static_cast<UChar>('\0'));
 }
 
-// See RFC 2616, Section 2.2.
+// See RFC 7230, Section 3.2.
+// Checks whether |value| matches field-content in RFC 7230.
+// link: http://tools.ietf.org/html/rfc7230#section-3.2
+bool isValidHTTPFieldContentRFC7230(const String& value)
+{
+    if (value.isEmpty())
+        return false;
+
+    UChar firstCharacter = value[0];
+    if (firstCharacter == ' ' || firstCharacter == '\t')
+        return false;
+
+    UChar lastCharacter = value[value.length() - 1];
+    if (lastCharacter == ' ' || lastCharacter == '\t')
+        return false;

[Mike West, 2015/09/02 06:59:14]

Why not just strip leading and trailing whitespace rather than yelling at
developers about them? :)

[shiva.jm, 2015/09/02 09:37:12]

striping of leading and trailing whitespace will be applied in another separate
CL after we measure the usage form these patch, as discussed in
https://codereview.chromium.org/1018903002/#msg31 and 
https://codereview.chromium.org/1018903002/#msg33

+
+    for (unsigned i = 0; i < value.length(); ++i) {

[Mike West, 2015/09/02 06:59:14]

Can you use the hot new C++11 loop syntax here? Not sure it works with strings,
so this is an honest question. :)

[shiva.jm, 2015/09/02 09:37:12]

tried using for ( UChar c : value), but got error:
invalid range expression of type 'const WTF::String'; no viable 'begin' function
available

+        UChar c = value[i];
+        if (c == 0x7F || c > 0xFF || (c < 0x20 && c != '\t'))

[Mike West, 2015/09/02 06:59:14]

This seems like it ought to already exist somewhere. Can you do a quick `git gs
'0x20'` to see where else we do this check? I suspect we can extract a character
class out of this.

[shiva.jm, 2015/09/02 09:37:12]

In these files same kind of check is done, WTFString.cpp GlyphPageTreeNode.cpp
Response.cpp Document.cpp 
CSSMarkup.cpp CSSPropertyParser.cpp

+            return false;
+    }
+
+    return true;
+}
+
+// See RFC 7230, Section 3.2.6.
 bool isValidHTTPToken(const String& characters)
 {
     if (characters.isEmpty())
         return false;
     for (unsigned i = 0; i < characters.length(); ++i) {
         UChar c = characters[i];
         if (c <= 0x20 || c >= 0x7F
             || c == '(' || c == ')' || c == '<' || c == '>' || c == '@'
             || c == ',' || c == ';' || c == ':' || c == '\\' || c == '"'
             || c == '/' || c == '[' || c == ']' || c == '?' || c == '='
@@ skipping 740 matching lines @@
 
 void parseCommaDelimitedHeader(const String& headerValue, CommaDelimitedHeaderSet& headerSet)
 {
     Vector<String> results;
     headerValue.split(",", results);
     for (auto& value : results)
         headerSet.add(value.stripWhiteSpace(isWhitespace));
 }
 
 }