Add support for case-insensitive attribute value selectors

Source/core/css/SelectorChecker.cpp

Index: Source/core/css/SelectorChecker.cpp
diff --git a/Source/core/css/SelectorChecker.cpp b/Source/core/css/SelectorChecker.cpp
index 8b93541c6efe4271a0b2cf596eb93420072e5499..e8fe8ab23b706651069df9e72648caa5a1b152ba 100644
--- a/Source/core/css/SelectorChecker.cpp
+++ b/Source/core/css/SelectorChecker.cpp
@@ -482,7 +482,8 @@ static bool anyAttributeMatches(Element& element, CSSSelector::Match match, cons
     if (!element.hasAttributesWithoutUpdate())
         return false;
 
-    const AtomicString& selectorValue =  selector.value();
+    const AtomicString& selectorValue = selector.value();
+    bool caseInsensitive = selector.attributeFlags() & CSSSelector::CaseInsensitive;
 
     unsigned attributeCount = element.attributeCount();
     for (size_t i = 0; i < attributeCount; ++i) {
@@ -491,9 +492,12 @@ static bool anyAttributeMatches(Element& element, CSSSelector::Match match, cons
         if (!attributeItem.matches(selectorAttr))
             continue;
 
-        if (attributeValueMatches(attributeItem, match, selectorValue, true))
+        if (attributeValueMatches(attributeItem, match, selectorValue, !caseInsensitive))
             return true;
 
+        if (caseInsensitive)
+            continue;
+
         // Case sensitivity for attribute matching is looser than hasAttribute or
         // Element::shouldIgnoreAttributeCase() for now. Unclear if that's correct.
         bool caseSensitive = !element.document().isHTMLDocument() || HTMLDocument::isCaseSensitiveAttribute(selectorAttr);