Add support for case-insensitive attribute value selectors

Source/core/css/parser/BisonCSSParser-in.cpp

Index: Source/core/css/parser/BisonCSSParser-in.cpp
diff --git a/Source/core/css/parser/BisonCSSParser-in.cpp b/Source/core/css/parser/BisonCSSParser-in.cpp
index 47147664df7f010bf46fc8eb8a5ffcd88c7e1db6..93196297bb5daabc237c8d82a8b515237e58610b 100644
--- a/Source/core/css/parser/BisonCSSParser-in.cpp
+++ b/Source/core/css/parser/BisonCSSParser-in.cpp
@@ -1124,6 +1124,17 @@ PassRefPtrWillBeRawPtr<MediaQuerySet> BisonCSSParser::parseMediaQueryList(const
     return m_mediaList.release();
 }
 
+bool BisonCSSParser::parseAttributeFlags(unsigned& flags, const String& string)
+{
+    if (!RuntimeEnabledFeatures::cssAttributeCaseSensitivityEnabled() && !isUASheetBehavior(m_context.mode()))
+        return false;
+    if (string == "i") {
+        flags = CSSSelector::CaseInsensitive;
+        return true;
+    }
+    return false;
+}
+
 static inline void filterProperties(bool important, const WillBeHeapVector<CSSProperty, 256>& input, WillBeHeapVector<CSSProperty, 256>& output, size_t& unusedEntries, BitArray<numCSSProperties>& seenProperties)
 {
     // Add properties in reverse order so that highest priority definitions are reached first. Duplicate definitions can then be ignored when found.