New parser mode for CSSOM @viewport descriptors.

Source/core/css/CSSParserMode.h

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 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:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
@@ skipping 26 matching lines @@
 
 class Document;
 
 enum CSSParserMode {
     CSSQuirksMode,
     CSSStrictMode,
     // SVG should always be in strict mode. For SVG attributes, the rules differ to strict sometimes.
     SVGAttributeMode,
     // User agent style sheet should always be in strict mode. Enables internal
     // only properties and values.
-    UASheetMode
+    UASheetMode,
+    // Parsing @viewport descriptors. Always strict.
+    ViewportMode

[eseidel, 2013/09/17 22:26:00]

If you're willing to go one more round here, it would be nice to have a comment
explaining what is different aboug this mode than others.  If it's just the
"width" thing, that seems easy to put in a comment.  If its complicated, we
could link to the spec.

[rune, 2013/09/18 08:13:09]

The main thing about this mode is to use viewport descriptor parsing rules
instead of style declaration parsing rules. While parsing a stylesheet, this is
triggered by setting inViewport() when the rule header (@viewport) is
encountered. This context is (or was) lost in the StylePropertySet, so modifying
the StylePropertySet through CSSOM would use the parsing rules for style
declarations instead of viewport descriptors.

I've extended/added comments.

 };
 
 inline CSSParserMode strictToCSSParserMode(bool inStrictMode)
 {
     return inStrictMode ? CSSStrictMode : CSSQuirksMode;
 }
 
 inline bool isStrictParserMode(CSSParserMode cssParserMode)
 {
-    return cssParserMode == CSSStrictMode || cssParserMode == SVGAttributeMode || cssParserMode == UASheetMode;
+    return cssParserMode != CSSQuirksMode;
 }
 
 struct CSSParserContext {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     CSSParserContext(CSSParserMode, const KURL& baseURL = KURL());
     CSSParserContext(const Document&, const KURL& baseURL = KURL(), const String& charset = emptyString());
 
     KURL baseURL;
     String charset;
@@ skipping 11 matching lines @@
 };
 
 bool operator==(const CSSParserContext&, const CSSParserContext&);
 inline bool operator!=(const CSSParserContext& a, const CSSParserContext& b) { return !(a == b); }
 
 const CSSParserContext& strictCSSParserContext();
 
 };
 
 #endif // CSSParserMode_h