cros: Update controlled-setting indicator text for Demo Mode

There are three places that use |IDS_CONTROLLED_SETTING_POLICY|, but
AFAIK there's no need to change the other two places
(arc_support_host.cc and extensions_ui.cc).

Bug: 873946
Change-Id: I34e9fb0a20139b0aaca6380e949248745f50ed58
Reviewed-on: https://chromium-review.googlesource.com/1180526Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584361}

chrome/app/chromeos_strings.grdp

@@ -2770,6 +2770,9 @@
   <message name="IDS_CONTROLLED_SETTING_SHARED" desc="Text displayed in the controlled settings bubble when a setting's value belongs to the primary user but can be edited.">
     This setting belongs to <ph name="OWNER_EMAIL">$1<ex>john@google.com</ex></ph>.
   </message>
+  <message name="IDS_CONTROLLED_SETTING_DEMO_SESSION" desc="Text displayed in the controlled settings bubble when a setting's value is enforced by demo session.">
+    This setting can't be changed in a demo session.
+  </message>
 
   <message name="IDS_STATUSBAR_DISABLE_SPOKEN_FEEDBACK" desc="The menu option to disable spoken feedback accessibility feature.">
     Disable ChromeVox (spoken feedback)

chrome/browser/ui/webui/policy_indicator_localized_strings_provider.cc

@@ -8,6 +8,10 @@
 #include "chrome/grit/generated_resources.h"
 #include "content/public/browser/web_ui_data_source.h"
 
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/login/demo_mode/demo_session.h"
+#endif
+
 namespace policy_indicator {
 
 struct LocalizedString {
@@ -16,8 +20,13 @@ struct LocalizedString {
 };
 
 void AddLocalizedStrings(content::WebUIDataSource* html_source) {
+  int controlled_setting_policy_id = IDS_CONTROLLED_SETTING_POLICY;
+#if defined(OS_CHROMEOS)
+  if (chromeos::DemoSession::IsDeviceInDemoMode())
+    controlled_setting_policy_id = IDS_CONTROLLED_SETTING_DEMO_SESSION;
+#endif
   LocalizedString localized_strings[] = {
-    {"controlledSettingPolicy", IDS_CONTROLLED_SETTING_POLICY},
+    {"controlledSettingPolicy", controlled_setting_policy_id},
     {"controlledSettingRecommendedMatches", IDS_CONTROLLED_SETTING_RECOMMENDED},
     {"controlledSettingRecommendedDiffers",
      IDS_CONTROLLED_SETTING_HAS_RECOMMENDATION},