GitLab

This changes ChromeVox language switching behavior to alert users
if we do not have an available voice for the current language, instead
of failing silently or butchering pronunciation with a different voice.
This change:
1. Adds logic in LanguageSwitching.js to check if there is a matching
voice for a language before making a language assignment
2. Modifies the accessibilityPrivate.getDisplayLanguage() api to
take an additional parameter (the desired output language)
3. Adds a LanguageSwitchingTest to confirm new behavior.
4. Modifies existing API tests to confirm new behavior.

Bug: 1008481
Change-Id: I5537c916a0e6b435c5c833b8e7fe7a9e530df65b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829547
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706050}