[Live Caption] Display SODA download progress updates in quick settings.

Screenshots:
- Soda install message in accessibility tray:
  https://screenshot.googleplex.com/9iRmn7Y6xpoVDxJ
- Soda error message in audio settings tray:
  https://screenshot.googleplex.com/Az5xt44wAVTmKLy
- Soda progress message in audio settings tray:
  https://screenshot.googleplex.com/5mnxpXcY6MMkP2A

Bug: 1196105
Change-Id: Ie7b5708355b6269d5c37a340959e039750ac4227
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3217417
Reviewed-by: Akihiro Ota <[email protected]>
Reviewed-by: James Cook <[email protected]>
Commit-Queue: Abigail Klein <[email protected]>
Cr-Commit-Position: refs/heads/main@{#987183}
diff --git a/ash/ash_prefs.cc b/ash/ash_prefs.cc
index cb1e2ef..4aa5c1a0 100644
--- a/ash/ash_prefs.cc
+++ b/ash/ash_prefs.cc
@@ -57,6 +57,7 @@
 #include "chromeos/services/assistant/public/cpp/assistant_prefs.h"
 #include "components/language/core/browser/pref_names.h"
 #include "components/live_caption/pref_names.h"
+#include "components/soda/constants.h"
 
 namespace ash {
 
@@ -117,6 +118,8 @@
     registry->RegisterBooleanPref(chromeos::prefs::kSuggestedContentEnabled,
                                   true);
     registry->RegisterBooleanPref(::prefs::kLiveCaptionEnabled, false);
+    registry->RegisterStringPref(::prefs::kLiveCaptionLanguageCode,
+                                 speech::kUsEnglishLocale);
     registry->RegisterStringPref(language::prefs::kApplicationLocale,
                                  std::string());
   }