arc: Limit locale/preferredLanguages for autotest.

In case arc-disable-locale-sync is used this limits ARC container to
start with 'en-US' as a locale and 'en-US,en' as preferred languages.
This stabilizes tests that expects UI resources be fixed in English.
There is an alternative solution that could be implemented when needed
to pass required combination as a switch. However this is not required
at this time once we don't have such auto-tests.

TEST=Set locale for local test account to 'ru' and confirmed that
cheets_AppCompatTest.clamshell.com.google.android.apps.books is failing
similar as described in bug. Apply this patch and test passes.
BUG=b:130142125

Change-Id: I2219207d2d75c00c6ee04590e430a929389c7319
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559463Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Yury Khmel <khmel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649236}

chrome/browser/chromeos/arc/arc_session_manager.cc

@@ -987,7 +987,15 @@ void ArcSessionManager::StartArc() {
 
   std::string locale;
   std::string preferred_languages;
-  GetLocaleAndPreferredLanguages(profile_, &locale, &preferred_languages);
+  if (IsArcLocaleSyncDisabled()) {
+    // Use fixed locale and preferred languages for auto-tests.
+    locale = "en-US";
+    preferred_languages = "en-US,en";
+    VLOG(1) << "Locale and preferred languages are fixed to " << locale << ","
+            << preferred_languages << ".";
+  } else {
+    GetLocaleAndPreferredLanguages(profile_, &locale, &preferred_languages);
+  }
 
   ArcSession::UpgradeParams params;
 

chromeos/constants/chromeos_switches.cc

@@ -106,7 +106,9 @@ const char kArcDisableAppSync[] = "arc-disable-app-sync";
 
 // Flag that disables ARC locale sync with Android container. Used in autotest
 // to prevent conditions when certain apps, including Play Store may get
-// restarted. Restarting Play Store may case random test failures.
+// restarted. Restarting Play Store may cause random test failures. Enabling
+// this flag would also forces ARC container to use 'en-US' as a locale and
+// 'en-US,en' as preferred languages.
 const char kArcDisableLocaleSync[] = "arc-disable-locale-sync";
 
 // Flag that disables ARC Play Auto Install flow that installs set of predefined