Revert of Improves focus/activation for aura-mus and DesktopNativeWidgetAura

ui/aura/mus/window_tree_client_delegate.h

Index: ui/aura/mus/window_tree_client_delegate.h
diff --git a/ui/aura/mus/window_tree_client_delegate.h b/ui/aura/mus/window_tree_client_delegate.h
index 5004d2c333af06e4619cf4e1b423af7a356e7ef7..5f58940c4fa9af1d9481362b79001e97107a66de 100644
--- a/ui/aura/mus/window_tree_client_delegate.h
+++ b/ui/aura/mus/window_tree_client_delegate.h
@@ -25,6 +25,7 @@
 
 namespace client {
 class CaptureClient;
+class FocusClient;
 }
 
 // Interface implemented by an application using mus.
@@ -59,6 +60,10 @@
   virtual void OnPointerEventObserved(const ui::PointerEvent& event,
                                       Window* target) = 0;
 
+  // Mus expects a single FocusClient is used for all WindowTreeHosts. This
+  // returns it. GetFocusClient() is called from the constructor.
+  virtual client::FocusClient* GetFocusClient() = 0;
+
   // Mus expects a single CaptureClient is used for all WindowTreeHosts. This
   // returns it. GetCaptureClient() is called from the constructor.
   virtual client::CaptureClient* GetCaptureClient() = 0;