Let StyleResolver figure out differences between UA style and resolved style.

Source/core/layout/LayoutTheme.cpp

Index: Source/core/layout/LayoutTheme.cpp
diff --git a/Source/core/layout/LayoutTheme.cpp b/Source/core/layout/LayoutTheme.cpp
index 5705d4167a046c771ed54632c8fb85e8bd0c811e..5d1fcddac720cc0c0820a9ce9890f3e7ff4fde3c 100644
--- a/Source/core/layout/LayoutTheme.cpp
+++ b/Source/core/layout/LayoutTheme.cpp
@@ -49,6 +49,7 @@
 #include "core/rendering/RenderMeter.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/style/RenderStyle.h"
+#include "core/rendering/style/UAStyleChange.h"
 #include "platform/FileMetadata.h"
 #include "platform/FloatConversion.h"
 #include "platform/RuntimeEnabledFeatures.h"
@@ -87,7 +88,7 @@ LayoutTheme::LayoutTheme()
 {
 }
 
-void LayoutTheme::adjustStyle(RenderStyle* style, Element* e, const CachedUAStyle* uaStyle)
+void LayoutTheme::adjustStyle(RenderStyle* style, Element* e, const UAStyleChange& uaStyle)
 {
     // Force inline and table display styles to be inline-block (except for table- which is block)
     ControlPart part = style->appearance();
@@ -99,7 +100,7 @@ void LayoutTheme::adjustStyle(RenderStyle* style, Element* e, const CachedUAStyl
     else if (style->display() == LIST_ITEM || style->display() == TABLE)
         style->setDisplay(BLOCK);
 
-    if (uaStyle && isControlStyled(style, uaStyle)) {
+    if (uaStyle.hasAppearance && isControlStyled(style, uaStyle)) {
         if (part == MenulistPart) {
             style->setAppearance(MenulistButtonPart);
             part = MenulistButtonPart;
@@ -545,25 +546,8 @@ bool LayoutTheme::isControlContainer(ControlPart appearance) const
     return appearance != CheckboxPart && appearance != RadioPart;
 }
 
-static bool isBackgroundOrBorderStyled(const RenderStyle& style, const CachedUAStyle& uaStyle)
+bool LayoutTheme::isControlStyled(const RenderStyle* style, const UAStyleChange& uaStyle) const
 {
-    // Code below excludes the background-repeat from comparison by resetting it
-    FillLayer backgroundCopy = uaStyle.backgroundLayers;
-    FillLayer backgroundLayersCopy = style.backgroundLayers();
-    backgroundCopy.setRepeatX(NoRepeatFill);
-    backgroundCopy.setRepeatY(NoRepeatFill);
-    backgroundLayersCopy.setRepeatX(NoRepeatFill);
-    backgroundLayersCopy.setRepeatY(NoRepeatFill);
-    // Test the style to see if the UA border and background match.
-    return style.border() != uaStyle.border
-        || backgroundLayersCopy != backgroundCopy
-        || style.visitedDependentColor(CSSPropertyBackgroundColor) != uaStyle.backgroundColor;
-}
-
-bool LayoutTheme::isControlStyled(const RenderStyle* style, const CachedUAStyle* uaStyle) const
-{
-    ASSERT(uaStyle);
-
     switch (style->appearance()) {
     case PushButtonPart:
     case SquareButtonPart:
@@ -574,13 +558,13 @@ bool LayoutTheme::isControlStyled(const RenderStyle* style, const CachedUAStyle*
     case ContinuousCapacityLevelIndicatorPart:
     case DiscreteCapacityLevelIndicatorPart:
     case RatingLevelIndicatorPart:
-        return isBackgroundOrBorderStyled(*style, *uaStyle);
+        return uaStyle.backgroundChanged || uaStyle.borderChanged;
 
     case MenulistPart:
     case SearchFieldPart:
     case TextAreaPart:
     case TextFieldPart:
-        return isBackgroundOrBorderStyled(*style, *uaStyle) || style->boxShadow();
+        return uaStyle.backgroundChanged || uaStyle.borderChanged || style->boxShadow();
 
     case SliderHorizontalPart:
     case SliderVerticalPart: