Simplify and add caching for accessible bounding box calculation.

Source/core/accessibility/AccessibilityObject.cpp

Index: Source/core/accessibility/AccessibilityObject.cpp
diff --git a/Source/core/accessibility/AccessibilityObject.cpp b/Source/core/accessibility/AccessibilityObject.cpp
index 89f493bcabf888e4dce21bd512383207f5322f1c..eb9bfe2143cd70bded08dc9e319666e570ade184 100644
--- a/Source/core/accessibility/AccessibilityObject.cpp
+++ b/Source/core/accessibility/AccessibilityObject.cpp
@@ -570,6 +570,12 @@ bool AccessibilityObject::isInsideARIALiveRegion() const
     return false;
 }
 
+void AccessibilityObject::markCachedElementRectDirty() const
+{
+    for (unsigned i = 0; i < m_children.size(); ++i)
+        m_children[i].get()->markCachedElementRectDirty();
+}
+
 IntPoint AccessibilityObject::clickPoint()
 {
     LayoutRect rect = elementRect();
@@ -787,7 +793,7 @@ bool AccessibilityObject::press() const
 
 void AccessibilityObject::scrollToMakeVisible() const
 {
-    IntRect objectRect = pixelSnappedIntRect(boundingBoxRect());
+    IntRect objectRect = pixelSnappedIntRect(elementRect());
     objectRect.setLocation(IntPoint());
     scrollToMakeVisibleWithSubFocus(objectRect);
 }
@@ -875,7 +881,7 @@ void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocu
     if (!scrollableArea)
         return;
 
-    LayoutRect objectRect = boundingBoxRect();
+    LayoutRect objectRect = elementRect();
     IntPoint scrollPosition = scrollableArea->scrollPosition();
     IntRect scrollVisibleRect = scrollableArea->visibleContentRect();
 
@@ -920,7 +926,7 @@ void AccessibilityObject::scrollToGlobalPoint(const IntPoint& globalPoint) const
 
         ScrollableArea* scrollableArea = outer->getScrollableAreaIfScrollable();
 
-        LayoutRect innerRect = inner->isAccessibilityScrollView() ? inner->parentObject()->boundingBoxRect() : inner->boundingBoxRect();
+        LayoutRect innerRect = inner->isAccessibilityScrollView() ? inner->parentObject()->elementRect() : inner->elementRect();
         LayoutRect objectRect = innerRect;
         IntPoint scrollPosition = scrollableArea->scrollPosition();