Use ASCII-caseless matching for attribute names.

third_party/WebKit/Source/platform/wtf/text/WTFString.cpp

Index: third_party/WebKit/Source/platform/wtf/text/WTFString.cpp
diff --git a/third_party/WebKit/Source/platform/wtf/text/WTFString.cpp b/third_party/WebKit/Source/platform/wtf/text/WTFString.cpp
index 9eb60a78b02b57e44ebd10c1a89389cbd4e11f6b..b200e854092e8e836edd038e5af175290c7037c1 100644
--- a/third_party/WebKit/Source/platform/wtf/text/WTFString.cpp
+++ b/third_party/WebKit/Source/platform/wtf/text/WTFString.cpp
@@ -294,6 +294,12 @@ String String::UpperUnicode(const AtomicString& locale_identifier) const {
   return impl_->UpperUnicode(locale_identifier);
 }
 
+String String::LowerASCII() const {
+  if (!impl_)
+    return String();
+  return impl_->LowerASCII();
+}
+
 String String::UpperASCII() const {
   if (!impl_)
     return String();