Add support for case-insensitive attribute value selectors

Source/core/css/CSSSelector.h

Index: Source/core/css/CSSSelector.h
diff --git a/Source/core/css/CSSSelector.h b/Source/core/css/CSSSelector.h
index 704cc4051339c98244edf12102fff23beba2a168..92f71bc633a1e24724e4dbef9f3e26205ff4d402 100644
--- a/Source/core/css/CSSSelector.h
+++ b/Source/core/css/CSSSelector.h
@@ -239,6 +239,11 @@ namespace blink {
             RightBottomMarginBox,
         };
 
+        enum AttributeFlags {
+            NoAttributeFlags,
+            CaseInsensitive,
+        };
+
         PseudoType pseudoType() const
         {
             if (m_pseudoType == PseudoNotParsed)
@@ -262,6 +267,7 @@ namespace blink {
         // how you use the returned QualifiedName.
         // http://www.w3.org/TR/css3-selectors/#attrnmsp
         const QualifiedName& attribute() const;
+        AttributeFlags attributeFlags() const;
         // Returns the argument of a parameterized selector. For example, nth-child(2) would have an argument of 2.
         const AtomicString& argument() const { return m_hasRareData ? m_data.m_rareData->m_argument : nullAtom; }
         const CSSSelectorList* selectorList() const { return m_hasRareData ? m_data.m_rareData->m_selectorList.get() : 0; }
@@ -272,7 +278,7 @@ namespace blink {
 #endif
 
         void setValue(const AtomicString&);
-        void setAttribute(const QualifiedName&);
+        void setAttribute(const QualifiedName&, unsigned flags);
         void setArgument(const AtomicString&);
         void setSelectorList(PassOwnPtr<CSSSelectorList>);
         void setMatchUserAgentOnly();
@@ -347,8 +353,14 @@ namespace blink {
             bool matchNth(int count);
 
             AtomicString m_value;
-            int m_a; // Used for :nth-*
-            int m_b; // Used for :nth-*
+            union Bits {

[eseidel, 2014/07/29 15:43:22]

I'm confused by these.  It looks like this is a big object, but I thoguht that
we had a ton of CSSSelector objects, so I would expect them to be size
sensitive, yet we haven't had a union before this one.

this feels like a half-hearte attempt to save space in this object, when we
probably could be more agressive. Can m_attribute and m_argument and m_value all
be used at the same time?  can m_selectorList?  Just confused that we are only
introducing a union now.  Feels like either we should continue to avoid the
union or unionize more of these attributes (in a separate patch).

[fs, 2014/07/29 17:14:32]

The union is "reaction" to comments in
https://codereview.chromium.org/252683011/ (the origin of this code). I don't
really have any data on with the frequencies of the different selector-types, so
this was mostly intended as an illustration of how the new field could be added
without affecting the "status quo" (memory-wise). I can revert the union-bit
again if requested (the fact that there's DataUnion in outer-class suggests to
me that this indeed rare data.)

(IIRC, the "groups" are (excluding the new field):

m_value+m_attribute
m_value+m_selectorList
m_value+m_argument+m_nth{A,B})

+                Bits() : m_nth() { }

[eseidel, 2014/07/29 15:43:22]

This doesn't do anything.

[fs, 2014/07/29 17:14:32]

It initializes m_nth to zeros.

+                struct {
+                    int m_a; // Used for :nth-*
+                    int m_b; // Used for :nth-*
+                } m_nth;
+                unsigned m_attributeFlags; // used for attribute selector (with value)
+            } m_bits;
             QualifiedName m_attribute; // used for attribute selector
             AtomicString m_argument; // Used for :contains, :lang, :nth-*
             OwnPtr<CSSSelectorList> m_selectorList; // Used for :-webkit-any and :not
@@ -373,6 +385,13 @@ inline const QualifiedName& CSSSelector::attribute() const
     return m_data.m_rareData->m_attribute;
 }
 
+inline CSSSelector::AttributeFlags CSSSelector::attributeFlags() const
+{
+    ASSERT(isAttributeSelector());
+    ASSERT(m_hasRareData);
+    return static_cast<AttributeFlags>(m_data.m_rareData->m_bits.m_attributeFlags);
+}
+
 inline bool CSSSelector::matchesPseudoElement() const
 {
     if (m_pseudoType == PseudoUnknown)