Android Accessibility: Avoiding Infinite loop of FrameLayouts in a11y tree

Initially https://chromium-review.googlesource.com/c/chromium/src/+/729145
ContentViewCore.java#b1735 shows that if the mWebContentsAccessibility was null or
not enabled, we just create it and enable it. The return value was null for these 2 cases.

This CL tries to get that behavior back and avoid loops.

Bug: 805014
Change-Id: I967503ec2601311c7bdd92b30bf5567308d4ce80
Reviewed-on: https://chromium-review.googlesource.com/891941
Commit-Queue: Isha Bobra <ibobra@google.com>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536404}
4 files changed