Fix crash in AutomationAXTreeWrapper::IsDesktopTree

Bug: 935963
Test: manual.
Change-Id: I7db0bc37d8085ac3f812818542d1a9dd6f8465de
Reviewed-on: https://chromium-review.googlesource.com/c/1489533
Auto-Submit: David Tseng <dtseng@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635682}
1 file changed