Simplify and add caching for accessible bounding box calculation.

Source/core/accessibility/AccessibilitySpinButton.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 47 matching lines @@
 AccessibilityObject* AccessibilitySpinButton::decrementButton()
 {
     if (!m_haveChildren)
         addChildren();
     
     ASSERT(m_children.size() == 2);
     
     return m_children[1].get();    
 }
     
-LayoutRect AccessibilitySpinButton::elementRect() const
+LayoutRect AccessibilitySpinButton::elementRect()
 {
     ASSERT(m_spinButtonElement);
     
     if (!m_spinButtonElement || !m_spinButtonElement->renderer())
         return LayoutRect();
     
     Vector<FloatQuad> quads;
     m_spinButtonElement->renderer()->absoluteFocusRingQuads(quads);
 
     return boundingBoxForQuads(m_spinButtonElement->renderer(), quads);
@@ skipping 28 matching lines @@
 AccessibilitySpinButtonPart::AccessibilitySpinButtonPart()
     : m_isIncrementor(false)
 {
 }
     
 PassRefPtr<AccessibilitySpinButtonPart> AccessibilitySpinButtonPart::create()
 {
     return adoptRef(new AccessibilitySpinButtonPart);
 }
 
-LayoutRect AccessibilitySpinButtonPart::elementRect() const
+LayoutRect AccessibilitySpinButtonPart::elementRect()
 {
     // FIXME: This logic should exist in the render tree or elsewhere, but there is no
     // relationship that exists that can be queried.
     
     LayoutRect parentRect = parentObject()->elementRect();
     if (m_isIncrementor)
         parentRect.setHeight(parentRect.height() / 2);
     else {
         parentRect.setY(parentRect.y() + parentRect.height() / 2);        
         parentRect.setHeight(parentRect.height() / 2);        
@@ skipping 10 matching lines @@
     AccessibilitySpinButton* spinButton = toAccessibilitySpinButton(parentObject());
     if (m_isIncrementor)
         spinButton->step(1);
     else
         spinButton->step(-1);
     
     return true;
 }
 
 } // namespace WebCore