Chromecast: return the correct locale in ContentBrowserClient.

R=byungchul@chromium.org,lcwu@chromium.org
BUG=336640

Review URL: https://codereview.chromium.org/517213005

Cr-Commit-Position: refs/heads/master@{#292737}

chromecast/shell/browser/cast_content_browser_client.cc

@@ -97,7 +97,8 @@ void CastContentBrowserClient::OverrideWebkitPrefs(
 }
 
 std::string CastContentBrowserClient::GetApplicationLocale() {
-  return "en-US";
+  const std::string locale(base::i18n::GetConfiguredLocale());
+  return locale.empty() ? "en-US" : locale;
 }
 
 void CastContentBrowserClient::AllowCertificateError(