Fix regression in msg id for ChromeVox

Regressing change
https://chromium-review.googlesource.com/c/chromium/src/+/1477455

- the msg id's get used in various other places (e.g. panel.js, command_store.js); changing them requires changing all uses of them
- the above change overwrote
https://chromium-review.googlesource.com/c/chromium/src/+/1512256

Test: make sure the ChromeVox Panel works.
Change-Id: I8074c000751ff6ab1e600615e68ca31a6686049e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1535002
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643428}
4 files changed