Fix handling of a case where an AccessibilityObject is listed as a child multiple times.

BUG=79726
TEST=browser_tests:RendererAccessibilityBrowserTest.CrossPlatformDuplicateChildrenAccessibility
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=82076
Review URL: http://codereview.chromium.org/6873063

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@82256 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed