Adding mojo calls for several lock screen related operations.

ash/public/interfaces/lock_screen.mojom

Index: ash/public/interfaces/lock_screen.mojom
diff --git a/ash/public/interfaces/lock_screen.mojom b/ash/public/interfaces/lock_screen.mojom
index 0b4a1417191f445f44e381bc5974d67cd0d8b3d5..c56393a3e438abf7fb73d36afacc6d87d9d4e555 100644
--- a/ash/public/interfaces/lock_screen.mojom
+++ b/ash/public/interfaces/lock_screen.mojom
@@ -74,6 +74,11 @@ interface LockScreen {
   // |users|:      A list of users who can unlock the device.
   // |show_guest|: Whether to show guest session button.
   LoadUsers(mojo.common.mojom.ListValue users, bool show_guest);
+  
+  // Requests to enable pin unlock for user in the user pod.

[jdufault, 2017/06/08 21:12:06]

nit: // Notification if pin is enabled or disabled for the given user.

[xiaoyinh(OOO Sep 11-29), 2017/06/09 00:47:10]

Thanks! Done.

+  // |account_id|:   The account id of the user in the user pod.
+  // |is_enabled|:   True if pin unlock is enabled.
+  SetPinEnabledForUser(signin.mojom.AccountId account_id, bool is_enabled);
 };
 
 // Allows ash lock screen to control a client (e.g. Chrome browser). Requests
@@ -102,4 +107,19 @@ interface LockScreenClient {
   // Record clicks on the lock icon in the user pod.
   // |account_id|:    The account id of the user in the user pod.
   RecordClickOnLockIcon(signin.mojom.AccountId account_id);
+  
+  // Focus user pod of user with |account_id|.
+  FocusPod(signin.mojom.AccountId account_id);
+  
+  // Notify that no user pod is focused.
+  NoPodFocused();
+  
+  // Load wallpaper of user with |account_id|.
+  LoadWallpaper(signin.mojom.AccountId account_id);
+  
+  // Sign out current user.
+  SignOutUser();
+  
+  // User with |account_id| has reached maximum incorrect password attempts.
+  MaxIncorrectPasswordAttempts(signin.mojom.AccountId account_id);
 };