Attempt to re-land FocusManager removal from Aura.

ui/views/corewm/focus_controller.cc

Index: ui/views/corewm/focus_controller.cc
diff --git a/ui/views/corewm/focus_controller.cc b/ui/views/corewm/focus_controller.cc
index a5fe9c3a7a96847e541cda15f1de09093caae9af..8c05ac26f324454016ad66d05224304424f5c2c8 100644
--- a/ui/views/corewm/focus_controller.cc
+++ b/ui/views/corewm/focus_controller.cc
@@ -179,15 +179,6 @@ aura::Window* FocusController::GetFocusedWindow() {
   return focused_window_;
 }
 
-void FocusController::OnWindowHiddenInRootWindow(
-    aura::Window* window,
-    aura::RootWindow* root_window,
-    bool destroyed) {
-  //NOTREACHED();
-  // This method is only for compat with aura::FocusManager. It should not be
-  // needed in the new FocusController.
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 // FocusController, ui::EventHandler implementation:
 void FocusController::OnKeyEvent(ui::KeyEvent* event) {