Merge 67418 - 2010-09-13 Chris Guillory <chris.guillory@google.com>...

Merge 67418 - 2010-09-13  Chris Guillory  <chris.guillory@google.com>;

        Reviewed by Chris Fleizach.

        WebAccessibilityCacheImpl needs to handle invalid accessibility object ids.
        https://bugs.webkit.org/show_bug.cgi?id=45572

        * public/WebAccessibilityObject.h:
        * src/WebAccessibilityCacheImpl.cpp:
        (WebKit::WebAccessibilityCacheImpl::addOrGetId):
        * src/WebAccessibilityObject.cpp:
        (WebKit::WebAccessibilityObject::isAxObjectIdValid):

TBR=ctguil@chromium.org
BUG=54973
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=67508