Implement canvas focus ring methods.

Source/core/accessibility/AccessibilityNodeObject.cpp

 /*
 * Copyright (C) 2012, Google 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 1166 matching lines @@
             if (role != GroupRole && role != UnknownRole)
                 break;
         }
     }
 
     return String();
 }
 
 LayoutRect AccessibilityNodeObject::elementRect() const
 {
+    // First check if it has a custom rect, for example if this element is tied to a canvas path.
+    if (!m_explicitElementRect.isEmpty())
+        return m_explicitElementRect;
+
     // AccessibilityNodeObjects have no mechanism yet to return a size or position.
     // For now, let's return the position of the ancestor that does have a position,
     // and make it the width of that parent, and about the height of a line of text, so that it's clear the object is a child of the parent.
 
     LayoutRect boundingBox;
 
     for (AccessibilityObject* positionProvider = parentObject(); positionProvider; positionProvider = positionProvider->parentObject()) {
         if (positionProvider->isAccessibilityRenderObject()) {
             LayoutRect parentRect = positionProvider->elementRect();
             boundingBox.setSize(LayoutSize(parentRect.width(), LayoutUnit(std::min(10.0f, parentRect.height().toFloat()))));
@@ skipping 469 matching lines @@
         useTextUnderElement = true;
 
     if (useTextUnderElement) {
         String text = textUnderElement();
         if (!text.isEmpty())
             textOrder.append(AccessibilityText(text, ChildrenText));
     }
 }
 
 } // namespace WebCore