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

Source/core/layout/LayoutTheme.h

 /*
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 11 matching lines @@
 
 #ifndef LayoutTheme_h
 #define LayoutTheme_h
 
 #if USE(NEW_THEME)
 #include "platform/Theme.h"
 #else
 #include "platform/ThemeTypes.h"
 #endif
 #include "core/rendering/RenderObject.h"
-#include "core/rendering/style/CachedUAStyle.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class Element;
 class FileList;
 class HTMLInputElement;
 class RenderMeter;
 class RenderProgress;
+class UAStyleChange;
 
 
 class LayoutTheme : public RefCounted<LayoutTheme> {
 protected:
     LayoutTheme();
 
 public:
     virtual ~LayoutTheme() { }
 
     // This function is to be implemented in your platform-specific theme implementation to hand back the
     // appropriate platform theme.
     static LayoutTheme& theme();
 
     static void setSizeIfAuto(RenderStyle*, const IntSize&);
 
     // This method is called whenever style has been computed for an element and the appearance
     // property has been set to a value other than "none".  The theme should map in all of the appropriate
     // metrics and defaults given the contents of the style.  This includes sophisticated operations like
     // selection of control size based off the font, the disabling of appearance when certain other properties like
     // "border" are set, or if the appearance is not supported by the theme.
-    void adjustStyle(RenderStyle*, Element*, const CachedUAStyle*);
+    void adjustStyle(RenderStyle*, Element*, const UAStyleChange&);
 
     // This method is called to paint the widget as a background of the RenderObject.  A widget's foreground, e.g., the
     // text of a button, is always rendered by the engine itself.  The boolean return value indicates
     // whether the CSS border/background should also be painted.
     bool paint(RenderObject*, const PaintInfo&, const IntRect&);
     bool paintBorderOnly(RenderObject*, const PaintInfo&, const IntRect&);
     bool paintDecorations(RenderObject*, const PaintInfo&, const IntRect&);
 
     // The remaining methods should be implemented by the platform-specific portion of the theme, e.g.,
     // LayoutThemeMac.cpp for Mac OS X.
 
     // These methods return the theme's extra style sheets rules, to let each platform
     // adjust the default CSS rules in html.css, quirks.css or mediaControls.css.
     virtual String extraDefaultStyleSheet();
     virtual String extraQuirksStyleSheet() { return String(); }
     virtual String extraMediaControlsStyleSheet() { return String(); }
     virtual String extraFullScreenStyleSheet() { return String(); }
 
     // A method to obtain the baseline position for a "leaf" control.  This will only be used if a baseline
     // position cannot be determined by examining child content. Checkboxes and radio buttons are examples of
     // controls that need to do this.
     virtual int baselinePosition(const RenderObject*) const;
 
     // A method for asking if a control is a container or not.  Leaf controls have to have some special behavior (like
     // the baseline position API above).
     bool isControlContainer(ControlPart) const;
 
     // Whether or not the control has been styled enough by the author to disable the native appearance.
-    virtual bool isControlStyled(const RenderStyle*, const CachedUAStyle*) const;
+    virtual bool isControlStyled(const RenderStyle*, const UAStyleChange&) const;
 
     // Some controls may spill out of their containers (e.g., the check on an OS X checkbox). When these controls issues paint invalidations,
     // the theme needs to communicate this inflated rect to the engine so that it can invalidate the whole control.
     virtual void adjustPaintInvalidationRect(const RenderObject*, IntRect&);
 
     // This method is called whenever a relevant state changes on a particular themed object, e.g., the mouse becomes pressed
     // or a control becomes disabled.
     virtual bool stateChanged(RenderObject*, ControlState) const;
 
     bool shouldDrawDefaultFocusRing(RenderObject*) const;
@@ skipping 202 matching lines @@
     static const RGBA32 defaultCompositionBackgroundColor = 0xFFFFDD55;
 
 #if USE(NEW_THEME)
     Theme* m_platformTheme; // The platform-specific theme.
 #endif
 };
 
 } // namespace blink
 
 #endif // LayoutTheme_h