AX: Use caching when requesting children object on iOS
https://bugs.webkit.org/show_bug.cgi?id=116112

Reviewed by David Kilzer.

Building up the children list in the AX hierarchy can be time consuming. On iOS, this
is now much more noticeable (I believe due to the way tables calculate their AX ignored flag).

We can speed everything up if we just cache the isIgnored() attribute while building up children.

* accessibility/AXObjectCache.cpp:
(WebCore::AXAttributeCacheEnabler::AXAttributeCacheEnabler):
(WebCore):
(WebCore::AXAttributeCacheEnabler::~AXAttributeCacheEnabler):
* accessibility/AXObjectCache.h:
(AXAttributeCacheEnabler):
(WebCore):
* accessibility/ios/WebAccessibilityObjectWrapperIOS.mm:
(-[WebAccessibilityObjectWrapper accessibilityHitTest:]):
(-[WebAccessibilityObjectWrapper accessibilityElementCount]):
(-[WebAccessibilityObjectWrapper accessibilityElementAtIndex:]):
(-[WebAccessibilityObjectWrapper indexOfAccessibilityElement:]):
(-[WebAccessibilityObjectWrapper accessibilityContainer]):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150145 268f45cc-cd09-0410-ab3c-d52691b4dbfc