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

ui/aura/env.h

Index: ui/aura/env.h
diff --git a/ui/aura/env.h b/ui/aura/env.h
index acd289b4c580e829932698ef9f9716ac5129edaf..d557a1f50f54d8f82d6276feaa940d017d1fb135 100644
--- a/ui/aura/env.h
+++ b/ui/aura/env.h
@@ -21,10 +21,6 @@
 class PlatformEventSource;
 }
 namespace aura {
-
-namespace client {
-class FocusClient;
-}
 
 namespace test {
 class EnvTestHelper;
@@ -78,17 +74,7 @@
   }
   ui::ContextFactory* context_factory() { return context_factory_; }
 
-  // Sets the active FocusClient and the window the FocusClient is associated
-  // with. |window| is not necessarily the window that actually has focus.
-  // |window| may be null, which indicates all windows share a FocusClient.
-  void SetActiveFocusClient(client::FocusClient* focus_client,
-                            Window* focus_client_root);
-  client::FocusClient* active_focus_client() { return active_focus_client_; }
-  Window* active_focus_client_root() { return active_focus_client_root_; }
-
  private:
-  class ActiveFocusClientWindowObserver;
-
   friend class test::EnvTestHelper;
   friend class Window;
   friend class WindowTreeHost;
@@ -105,8 +91,6 @@
 
   // Invoked by WindowTreeHost when it is activated. Notifies observers.
   void NotifyHostActivated(WindowTreeHost* host);
-
-  void OnActiveFocusClientWindowDestroying();
 
   // Overridden from ui::EventTarget:
   bool CanAcceptEvent(const ui::Event& event) override;
@@ -128,11 +112,6 @@
 
   ui::ContextFactory* context_factory_;
 
-  Window* active_focus_client_root_ = nullptr;
-  client::FocusClient* active_focus_client_ = nullptr;
-  std::unique_ptr<ActiveFocusClientWindowObserver>
-      active_focus_client_window_observer_;
-
   DISALLOW_COPY_AND_ASSIGN(Env);
 };