Simplify and add caching for accessible bounding box calculation.

Source/core/accessibility/AccessibilityRenderObject.h

Index: Source/core/accessibility/AccessibilityRenderObject.h
diff --git a/Source/core/accessibility/AccessibilityRenderObject.h b/Source/core/accessibility/AccessibilityRenderObject.h
index 839c24c4f99a1a83b5c01e4ba37007e052def8da..6871bf64e18cb10daeb65d4a3a66c4109f0d18ed 100644
--- a/Source/core/accessibility/AccessibilityRenderObject.h
+++ b/Source/core/accessibility/AccessibilityRenderObject.h
@@ -63,11 +63,9 @@ public:
     static PassRefPtr<AccessibilityRenderObject> create(RenderObject*);
     virtual ~AccessibilityRenderObject();
 
-    RenderObject* m_renderer;
-
     // Public, overridden from AccessibilityObject.
     virtual RenderObject* renderer() const { return m_renderer; }
-    virtual LayoutRect elementRect() const;
+    virtual LayoutRect elementRect();

[Julien - ping for review, 2013/05/03 20:54:20]

FWIW I would have kept this const because you still match the definition of
logical constness (you're only updating your cache). That means making the
caching related members 'mutable'.

[dmazzoni, 2013/05/06 04:58:01]

Great idea, that simplifies things a lot.

 
     // DEPRECATED - investigate and remove.
     virtual int layoutCount() const;
@@ -83,6 +81,11 @@ public:
     virtual AccessibilityRole determineAccessibilityRole();
 
 protected:
+    RenderObject* m_renderer;
+    LayoutRect m_cachedElementRect;
+    LayoutRect m_cachedFrameRect;
+    bool m_cachedElementRectDirty;
+
     //
     // Overridden from AccessibilityObject.
     //
@@ -130,7 +133,7 @@ protected:
     virtual AccessibilityObject* correspondingLabelForControlElement() const;
     virtual bool exposesTitleUIElement() const;
     virtual void linkedUIElements(AccessibilityChildrenVector&) const;
-    virtual AccessibilityOrientation orientation() const;
+    virtual AccessibilityOrientation orientation();
     virtual void tabChildren(AccessibilityChildrenVector&);
     virtual String text() const;
     virtual int textLength() const;
@@ -140,7 +143,6 @@ protected:
 
     // Properties of interactive elements.
     virtual const String& actionVerb() const;
-    LayoutRect checkboxOrRadioRect() const;
     virtual void selectedChildren(AccessibilityChildrenVector&);
     virtual String stringValue() const;
 
@@ -171,13 +173,14 @@ protected:
     // Accessibility Text - (To be deprecated).
     virtual String helpText() const;
 
-    // Position and size.
-    virtual LayoutRect boundingBoxRect() const;
+    // Location and click point in frame-relative coordinates.
+    virtual void updateCachedElementRect();
+    virtual void markCachedElementRectDirty();
     virtual IntPoint clickPoint();
 
     // Hit testing.
     virtual AccessibilityObject* accessibilityHitTest(const IntPoint&) const;
-    virtual AccessibilityObject* elementAccessibilityHitTest(const IntPoint&) const;
+    virtual AccessibilityObject* elementAccessibilityHitTest(const IntPoint&);
 
     // High-level accessibility tree access. Other modules should only use these functions.
     virtual AccessibilityObject* parentObject() const;
@@ -261,7 +264,7 @@ private:
     bool isSVGImage() const;
     void detachRemoteSVGRoot();
     AccessibilitySVGRoot* remoteSVGRootElement() const;
-    AccessibilityObject* remoteSVGElementHitTest(const IntPoint&) const;
+    AccessibilityObject* remoteSVGElementHitTest(const IntPoint&);
     void offsetBoundingBoxForRemoteSVGElement(LayoutRect&) const;
     void addHiddenChildren();
     void addTextFieldChildren();
@@ -272,6 +275,7 @@ private:
     void ariaSelectedRows(AccessibilityChildrenVector&);
     bool elementAttributeValue(const QualifiedName&) const;
     bool inheritsPresentationalRole() const;
+    LayoutRect computeElementRect();

[Julien - ping for review, 2013/05/03 20:54:20]

This method should really be const as you wouldn't expect it to actually modify
the object. It's unfortunate some of the called APIs are not const for no good
reason I could think about.

[dmazzoni, 2013/05/06 04:58:01]

Done.

 };
 
 inline AccessibilityRenderObject* toAccessibilityRenderObject(AccessibilityObject* object)