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

ui/views/mus/desktop_window_tree_host_mus.h

Index: ui/views/mus/desktop_window_tree_host_mus.h
diff --git a/ui/views/mus/desktop_window_tree_host_mus.h b/ui/views/mus/desktop_window_tree_host_mus.h
index 9aba79c1e46864114f04b215de5939f04c66c27c..9893ed613458b6f24754756e6b0c6395ed8b60cf 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.h
+++ b/ui/views/mus/desktop_window_tree_host_mus.h
@@ -9,7 +9,6 @@
 #include <set>
 
 #include "base/macros.h"
-#include "ui/aura/env_observer.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/views/mus/mus_export.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host.h"
@@ -18,8 +17,7 @@
 
 class VIEWS_MUS_EXPORT DesktopWindowTreeHostMus
     : public DesktopWindowTreeHost,
-      public aura::WindowTreeHostMus,
-      public aura::EnvObserver {
+      public aura::WindowTreeHostMus {
  public:
   DesktopWindowTreeHostMus(
       internal::NativeWidgetDelegate* native_widget_delegate,
@@ -90,11 +88,6 @@
   bool IsTranslucentWindowOpacitySupported() const override;
   void SizeConstraintsChanged() override;
 
-  // aura::EnvObserver:
-  void OnWindowInitialized(aura::Window* window) override;
-  void OnActiveFocusClientChanged(aura::client::FocusClient* focus_client,
-                                  aura::Window* window) override;
-
   internal::NativeWidgetDelegate* native_widget_delegate_;
 
   DesktopNativeWidgetAura* desktop_native_widget_aura_;
@@ -108,8 +101,6 @@
   DesktopWindowTreeHostMus* parent_ = nullptr;
   std::set<DesktopWindowTreeHostMus*> children_;
 
-  bool is_active_ = false;
-
   // Used so that Close() isn't immediate.
   base::WeakPtrFactory<DesktopWindowTreeHostMus> close_widget_factory_;