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..f6e32ba9b7104b5c5467a6218b5613549d676396 100644
--- a/Source/core/accessibility/AccessibilityObject.cpp
+++ b/Source/core/accessibility/AccessibilityObject.cpp
@@ -353,7 +353,7 @@ int AccessibilityObject::blockquoteLevel() const
 }
 
 // Lacking concrete evidence of orientation, horizontal means width > height. vertical is height > width;
-AccessibilityOrientation AccessibilityObject::orientation() const
+AccessibilityOrientation AccessibilityObject::orientation()
 {
     LayoutRect bounds = elementRect();
     if (bounds.size().width() > bounds.size().height())
@@ -570,6 +570,14 @@ bool AccessibilityObject::isInsideARIALiveRegion() const
     return false;
 }
 
+void AccessibilityObject::markCachedElementRectDirty()
+{
+    AccessibilityChildrenVector axChildren = children();
+    for (unsigned i = 0; i < axChildren.size(); ++i) {
+        axChildren[i].get()->markCachedElementRectDirty();
+    }
+}
+
 IntPoint AccessibilityObject::clickPoint()
 {
     LayoutRect rect = elementRect();
@@ -598,7 +606,7 @@ IntRect AccessibilityObject::boundingBoxForQuads(RenderObject* obj, const Vector
     return result;
 }
 
-AccessibilityObject* AccessibilityObject::elementAccessibilityHitTest(const IntPoint& point) const
+AccessibilityObject* AccessibilityObject::elementAccessibilityHitTest(const IntPoint& point)
 {
     // Send the hit test back into the sub-frame if necessary.
     if (isAttachment()) {
@@ -785,9 +793,9 @@ bool AccessibilityObject::press() const
     return true;
 }
 
-void AccessibilityObject::scrollToMakeVisible() const
+void AccessibilityObject::scrollToMakeVisible()
 {
-    IntRect objectRect = pixelSnappedIntRect(boundingBoxRect());
+    IntRect objectRect = pixelSnappedIntRect(elementRect());
     objectRect.setLocation(IntPoint());
     scrollToMakeVisibleWithSubFocus(objectRect);
 }
@@ -864,7 +872,7 @@ static int computeBestScrollOffset(int currentScrollOffset,
     return currentScrollOffset;
 }
 
-void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocus) const
+void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocus)
 {
     // Search up the parent chain until we find the first one that's scrollable.
     AccessibilityObject* scrollParent = parentObject();
@@ -875,7 +883,7 @@ void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocu
     if (!scrollableArea)
         return;
 
-    LayoutRect objectRect = boundingBoxRect();
+    LayoutRect objectRect = elementRect();
     IntPoint scrollPosition = scrollableArea->scrollPosition();
     IntRect scrollVisibleRect = scrollableArea->visibleContentRect();
 
@@ -897,11 +905,11 @@ void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocu
         scrollParent->scrollToMakeVisible();
 }
 
-void AccessibilityObject::scrollToGlobalPoint(const IntPoint& globalPoint) const
+void AccessibilityObject::scrollToGlobalPoint(const IntPoint& globalPoint)
 {
     // Search up the parent chain and create a vector of all scrollable parent objects
     // and ending with this object itself.
-    Vector<const AccessibilityObject*> objects;
+    Vector<AccessibilityObject*> objects;
     AccessibilityObject* parentObject;
     for (parentObject = this->parentObject(); parentObject; parentObject = parentObject->parentObject()) {
         if (parentObject->getScrollableAreaIfScrollable())
@@ -915,12 +923,12 @@ void AccessibilityObject::scrollToGlobalPoint(const IntPoint& globalPoint) const
     IntPoint point = globalPoint;
     size_t levels = objects.size() - 1;
     for (size_t i = 0; i < levels; i++) {
-        const AccessibilityObject* outer = objects[i];
-        const AccessibilityObject* inner = objects[i + 1];
+        AccessibilityObject* outer = objects[i];
+        AccessibilityObject* inner = objects[i + 1];
 
         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();