Implement hit tests/client area.

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 38c9ebb4f860722cc0b12146d9cf314d8596f9b2..8cecf2b234fe9fb7836bacdfce4152cc13246829 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.h
+++ b/ui/views/mus/desktop_window_tree_host_mus.h
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
+#include "ui/views/mus/mus_client_observer.h"
 #include "ui/views/mus/mus_export.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host.h"
 #include "ui/views/widget/widget.h"
@@ -19,6 +20,7 @@ namespace views {
 
 class VIEWS_MUS_EXPORT DesktopWindowTreeHostMus
     : public DesktopWindowTreeHost,
+      public MusClientObserver,
       public aura::WindowTreeHostMus,
       public aura::EnvObserver {
  public:
@@ -31,6 +33,9 @@ class VIEWS_MUS_EXPORT DesktopWindowTreeHostMus
  private:
   bool IsDocked() const;
 
+  void UpdateClientArea();
+  void UpdateHitTestMask();
+
   // DesktopWindowTreeHost:
   void Init(aura::Window* content_window,
             const Widget::InitParams& params) override;
@@ -92,6 +97,9 @@ class VIEWS_MUS_EXPORT DesktopWindowTreeHostMus
   bool IsTranslucentWindowOpacitySupported() const override;
   void SizeConstraintsChanged() override;
 
+  // MusClientObserver:
+  void OnWindowManagerFrameValuesChanged() override;
+
   // WindowTreeHostMus:
   void ShowImpl() override;
   void HideImpl() override;