cros: Fixed 3 bugs for pin unlock.

ui/login/account_picker/screen_account_picker.js

Index: ui/login/account_picker/screen_account_picker.js
diff --git a/ui/login/account_picker/screen_account_picker.js b/ui/login/account_picker/screen_account_picker.js
index 69c5eafe3dbb55e5b6523da09c79a181a2be8fd0..698bc87c876a2d8f0e0bedcb37f6f0f5cf66fbf6 100644
--- a/ui/login/account_picker/screen_account_picker.js
+++ b/ui/login/account_picker/screen_account_picker.js
@@ -224,15 +224,20 @@ login.createScreen('AccountPickerScreen', 'account-picker', function() {
     },
 
     /**
-     * Loads the PIN keyboard if any of the users can login with a PIN.
+     * Loads the PIN keyboard if any of the users can login with a PIN. Disables
+     * the PIN keyboard for users who are not allowed to use PIN unlock.
      * @param {array} users Array of user instances.
      */
-    loadPinKeyboardIfNeeded_: function(users) {
+    initializePinKeyboardStateForUsers_: function(users) {
       for (var i = 0; i < users.length; ++i) {
         var user = users[i];
         if (user.showPin) {
           showPinKeyboardAsync();
-          return;
+        } else {
+          // Disable pin for users which should not be able to access pin. Such
+          // users include those who have not set up pin as those who have not

[jdufault, 2016/10/21 19:09:56]

I'm not sure we need to include a comment here. If you want to keep it, please
cleanup it a little, ie:

  // Disable PIN for users which cannot authenticate with it. For 
  // example, users who have not set up PIN or users who have not
  // entered their account password recently.

This comment explains the user.showPin value - I'm not sure that variable is
confusing, though. If anything, we should be explaining why we want to
explicitly call disableKeyboardForUser, ie, if we do not, then the PIN keyboard
can appear when there are >1 users.

[sammiequon, 2016/10/21 22:07:51]

Done.

+          // entered their password recently.
+          this.disablePinKeyboardForUser(user.username);
         }
       }
     },
@@ -249,7 +254,7 @@ login.createScreen('AccountPickerScreen', 'account-picker', function() {
       if (Oobe.getInstance().displayType == DISPLAY_TYPE.DESKTOP_USER_MANAGER)
         $('login-header-bar').classList.toggle('shadow', users.length > 8);
 
-      this.loadPinKeyboardIfNeeded_(users);
+      this.initializePinKeyboardStateForUsers_(users);
     },
 
     /**