chromeos: removes unused function

No one overrides MultiUserWindowManager::Observer::OnOwnerEntryFinished.

BUG=756085
TEST=none

Change-Id: If91a4e3fc4c5d63ef762763534b93865466ae833
Reviewed-on: https://chromium-review.googlesource.com/c/1323621Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606140}

chrome/browser/ui/ash/multi_user/multi_user_window_manager.h

@@ -44,9 +44,6 @@ class MultiUserWindowManager {
     virtual void OnOwnerEntryAdded(aura::Window* window) {}
     // Invoked when the owner of the window tracked by the manager is changed.
     virtual void OnOwnerEntryChanged(aura::Window* window) {}
-    // Invoked when the window is destroyed and the manager stop to track its
-    // owner.
-    virtual void OnOwnerEntryRemoved(aura::Window* window) {}
     // Invoked when the user switch animation is finished.
     virtual void OnUserSwitchAnimationFinished() {}
 

chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc

@@ -424,10 +424,6 @@ void MultiUserWindowManagerChromeOS::OnWindowDestroyed(aura::Window* window) {
   // Remove the window from the owners list.
   delete window_to_entry_[window];
   window_to_entry_.erase(window);
-
-  // Notify entry change.
-  for (Observer& observer : observers_)
-    observer.OnOwnerEntryRemoved(window);
 }
 
 void MultiUserWindowManagerChromeOS::OnWindowVisibilityChanging(