Have srcset respond to viewport changes

Source/core/css/parser/SizesAttributeParser.h

 // 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.
 
 #ifndef SizesAttributeParser_h
 #define SizesAttributeParser_h
 
 #include "core/css/MediaValues.h"
 #include "core/css/parser/MediaQueryParser.h"
 #include "platform/heap/Handle.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class SizesAttributeParser {
     STACK_ALLOCATED();
 public:
-    static unsigned findEffectiveSize(const String& attribute, PassRefPtr<MediaValues>);
+    SizesAttributeParser(PassRefPtr<MediaValues>, const String&);
+
+    bool viewportDependant() const { return m_viewportDependant; }
+    unsigned length();
 
 private:
-    SizesAttributeParser(PassRefPtr<MediaValues> mediaValues)
-        : m_mediaValues(mediaValues)
-        , m_length(0)
-        , m_lengthWasSet(false)
-    {
-    }
-
     bool parse(Vector<MediaQueryToken>& tokens);
     bool parseMediaConditionAndLength(MediaQueryTokenIterator startToken, MediaQueryTokenIterator endToken);
     unsigned effectiveSize();
     bool calculateLengthInPixels(MediaQueryTokenIterator startToken, MediaQueryTokenIterator endToken, unsigned& result);
     bool mediaConditionMatches(PassRefPtrWillBeRawPtr<MediaQuerySet> mediaCondition);
     unsigned effectiveSizeDefaultValue();
 
     RefPtrWillBeMember<MediaQuerySet> m_mediaCondition;
     RefPtr<MediaValues> m_mediaValues;
     unsigned m_length;
     bool m_lengthWasSet;
+    bool m_viewportDependant;
+    Vector<MediaQueryToken> m_tokens;
+    bool m_isValid;
 };
 
 } // namespace
 
 #endif