Split out String, URI and CustomIdent from CSSPrimitiveValue

Source/core/css/RuleFeature.cpp

Index: Source/core/css/RuleFeature.cpp
diff --git a/Source/core/css/RuleFeature.cpp b/Source/core/css/RuleFeature.cpp
index 6aecffc6a099cd6c7527f86d4f0ecffdc5067de7..53ea3d5840edfb462aa0a9269145f6474f79f21f 100644
--- a/Source/core/css/RuleFeature.cpp
+++ b/Source/core/css/RuleFeature.cpp
@@ -33,6 +33,7 @@
 #include "core/css/CSSFunctionValue.h"
 #include "core/css/CSSSelector.h"
 #include "core/css/CSSSelectorList.h"
+#include "core/css/CSSStringValue.h"
 #include "core/css/CSSValueList.h"
 #include "core/css/RuleSet.h"
 #include "core/css/StylePropertySet.h"
@@ -316,7 +317,7 @@ void RuleFeatureSet::updateInvalidationSetsForContentAttribute(const RuleData& r
         CSSFunctionValue* functionValue = toCSSFunctionValue(item.get());
         if (functionValue->functionType() != CSSValueAttr)
             continue;
-        ensureAttributeInvalidationSet(AtomicString(toCSSPrimitiveValue(functionValue->item(0))->getStringValue()));
+        ensureAttributeInvalidationSet(AtomicString(toCSSStringValue(functionValue->item(0))->getStringValue()));
     }
 }