Reland Fire appropriate events when the accessibility caret has been created or destroyed

Fixed use-after-free bug.
> Bug: 792820
R=dmazzoni@chromium.org, ananta@chromium.org
Tested: using syzyASAN

Change-Id: I0bc1dd2ed9f8bbe788b5ce89e7290467698a6c58
Reviewed-on: https://chromium-review.googlesource.com/818034
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523013}
1 file changed