chromeos: Replace user image notifications with observer

components/user_manager/user_manager.h

Index: components/user_manager/user_manager.h
diff --git a/components/user_manager/user_manager.h b/components/user_manager/user_manager.h
index 8104d7615bfb7d886c265451484cde2b3bb16ab5..fbf4cc185bf66865199b23ff1c50a531d5b03759 100644
--- a/components/user_manager/user_manager.h
+++ b/components/user_manager/user_manager.h
@@ -39,6 +39,18 @@ class USER_MANAGER_EXPORT UserManager {
     // Called when the local state preferences is changed.
     virtual void LocalStateChanged(UserManager* user_manager);
 
+    // Called when the image of the given user is changed.
+    virtual void OnUserImageChanged(const User& user);
+
+    // Called when the profile image download for the given user fails or
+    // user has the default profile image or no porfile image at all.
+    virtual void OnUserProfileImageUpdateFailed(const User& user);
+
+    // Called when the profile image for the given user is downloaded.
+    // |profile_image| contains the downloaded profile image.
+    virtual void OnUserProfileImageUpdated(const User& user,
+                                           const gfx::ImageSkia& profile_image);
+
    protected:
     virtual ~Observer();
   };
@@ -300,6 +312,11 @@ class USER_MANAGER_EXPORT UserManager {
   virtual void RemoveSessionStateObserver(UserSessionStateObserver* obs) = 0;
 
   virtual void NotifyLocalStateChanged() = 0;
+  virtual void NotifyUserImageChanged(const User& user) = 0;
+  virtual void NotifyUserProfileImageUpdateFailed(const User& user) = 0;
+  virtual void NotifyUserProfileImageUpdated(
+      const User& user,
+      const gfx::ImageSkia& profile_image) = 0;
 
   // Changes the child status and notifies observers.
   virtual void ChangeUserChildStatus(User* user, bool is_child) = 0;