[wip] simplify -webkit-appearance adjust step

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index 8fd045ef3711a43e5d7e64e6e9ff6d649ed43ec5..33a76811157a54228b639993b7121468748f2614 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -593,7 +593,8 @@ static void addContentAttrValuesToFeatures(const Vector<AtomicString>& contentAt
 void StyleResolver::adjustRenderStyle(StyleResolverState& state, Element* element)
 {
     StyleAdjuster adjuster(m_document.inQuirksMode());
-    adjuster.adjustRenderStyle(state.style(), state.parentStyle(), element, state.cachedUAStyle());
+    bool uaStyleHasWebkitAppearance = element && elementTypeHasAppearanceFromUAStyle(*element);
+    adjuster.adjustRenderStyle(state.style(), state.parentStyle(), element, uaStyleHasWebkitAppearance, state.valuesUnchangedForWebkitAppearance());
 }
 
 // Start loading resources referenced by this style.
@@ -1165,13 +1166,9 @@ void StyleResolver::applyMatchedProperties(StyleResolverState& state, const Matc
 
     // This code supports -webkit-appearance, for which we are interested
     // in whether the user has specified border or background properties.
-    // FIXME: This is a bit of a mess, we should just compare CSSValues and
-    // store a single bit for this.
     if (elementTypeHasAppearanceFromUAStyle(*element)) {
-        CascadedValues userAgentValues(state, matchResult, true);
-        // We only actually care about border and background properties here
-        userAgentValues.applyValues(firstCSSPropertyId<LowPriorityProperties>(), lastCSSPropertyId<LowPriorityProperties>(), applyInheritedOnly);
-        state.cacheUserAgentBorderAndBackground();
+        if (cascadedValues.valuesUnchangedForWebkitAppearance(matchResult))
+            state.setValuesUnchangedForWebkitAppearance();
     }
 
     cascadedValues.applyValues(firstCSSPropertyId<LowPriorityProperties>(), lastCSSPropertyId<LowPriorityProperties>(), applyInheritedOnly);