Don't send extra text changed AX events on Android (2)

Follow-up to https://codereview.chromium.org/920623002/ - this change is
also needed.

BUG=457903
TBR=plundblad@chromium.org

Review URL: https://codereview.chromium.org/922883002

Cr-Commit-Position: refs/heads/master@{#316071}
1 file changed