MD User Manager: Display error message when all profiles are locked.

chrome/browser/resources/md_user_manager/profile_browser_proxy.js

Index: chrome/browser/resources/md_user_manager/profile_browser_proxy.js
diff --git a/chrome/browser/resources/md_user_manager/profile_browser_proxy.js b/chrome/browser/resources/md_user_manager/profile_browser_proxy.js
index 2bc9630db21fd8c1627e2642f895b07115f94be9..cd9173915e35bc961f5d4dcecdb4071b7427d110 100644
--- a/chrome/browser/resources/md_user_manager/profile_browser_proxy.js
+++ b/chrome/browser/resources/md_user_manager/profile_browser_proxy.js
@@ -118,6 +118,15 @@ cr.define('signin', function() {
      */
     switchToProfile: function(profilePath) {
       assertNotReached();
+    },
+
+    /**
+     * Returns a Promise that is resolved with a true value if at all
+     * (non-supervised and non-child) profiles are locked.
+     * @return {Promise}

[dpapad, 2016/05/31 21:05:51]

The type annotation can be more specific, and also the entire comment can be
shortened as follows.

/**
 * @return {!Promise<boolean>} Whether all (non-supervised and non-child)
 *     profiles are locked.
 */

[Moe, 2016/05/31 22:14:05]

Done.

+     */
+    areAllProfilesLocked: function() {
+      assertNotReached();
     }
   };
 
@@ -183,6 +192,11 @@ cr.define('signin', function() {
     /** @override */
     switchToProfile: function(profilePath) {
       chrome.send('switchToProfile', [profilePath]);
+    },
+
+    /** @override */
+    areAllProfilesLocked: function() {
+      return cr.sendWithPromise('areAllProfilesLocked');
     }
   };