The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/21b7e9dc357019b0d715281d95032734993d4749

commit 21b7e9dc357019b0d715281d95032734993d4749
Author: Katie D <katie@chromium.org>
Date: Wed Oct 17 19:50:30 2018

Stop explicity picking a locale if not otherwise specified.

Chromevox does not need to specify a locale the current language if
it isn't already specified by the user. This is already done by
the TTS controller. If Chromevox also choses a locale we end up
doing matching on the locale before the voice, and Chromevox does
not appear to use the default system voice.

Bug:  896321 
Change-Id: I0ea4919aaf24dd52a72f552b93c4d7490a188ef2
Reviewed-on: https://chromium-review.googlesource.com/c/1286932
Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600524}
[modify] https://crrev.com/21b7e9dc357019b0d715281d95032734993d4749/chrome/browser/resources/chromeos/chromevox/host/chrome/tts_background.js