Reland: Show message center on lock screen

ui/message_center/message_center.h

Index: ui/message_center/message_center.h
diff --git a/ui/message_center/message_center.h b/ui/message_center/message_center.h
index 038c7b712e622f18f021f78fddb28f8f3084c669..6db00a2e322d8a1709ce8791e8f06a702d8fa15f 100644
--- a/ui/message_center/message_center.h
+++ b/ui/message_center/message_center.h
@@ -76,6 +76,7 @@ class MESSAGE_CENTER_EXPORT MessageCenter {
   virtual size_t UnreadNotificationCount() const = 0;
   virtual bool HasPopupNotifications() const = 0;
   virtual bool IsQuietMode() const = 0;
+  virtual bool IsLockedState() const = 0;
   virtual bool HasClickedListener(const std::string& id) = 0;
 
   // Find the notification with the corresponding id. Returns NULL if not found.
@@ -171,6 +172,9 @@ class MESSAGE_CENTER_EXPORT MessageCenter {
   // This can be called to change the quiet mode state (without a timeout).
   virtual void SetQuietMode(bool in_quiet_mode) = 0;
 
+  // This can be called to change the lock mode state.
+  virtual void SetLockedState(bool locked) = 0;
+
   // Temporarily enables quiet mode for |expires_in| time.
   virtual void EnterQuietModeWithExpire(const base::TimeDelta& expires_in) = 0;