Updates shadow when active window changes

components/mus/public/cpp/lib/window_tree_client_impl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_MUS_PUBLIC_CPP_LIB_WINDOW_TREE_CLIENT_IMPL_H_
 #define COMPONENTS_MUS_PUBLIC_CPP_LIB_WINDOW_TREE_CLIENT_IMPL_H_
 
 #include <map>
 
+#include "base/observer_list.h"
 #include "components/mus/common/types.h"
 #include "components/mus/public/cpp/window.h"
 #include "components/mus/public/cpp/window_tree_connection.h"
 #include "components/mus/public/interfaces/window_tree.mojom.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace gfx {
 class Insets;
 class Size;
 }
@@ skipping 102 matching lines @@
                    Id focused_window_id,
                    uint32 access_policy);
 
   // Overridden from WindowTreeConnection:
   Window* GetRoot() override;
   Window* GetWindowById(Id id) override;
   Window* GetFocusedWindow() override;
   Window* NewWindow(const Window::SharedProperties* properties) override;
   bool IsEmbedRoot() override;
   ConnectionSpecificId GetConnectionId() override;
+  void AddObserver(WindowTreeConnectionObserver* observer) override;
+  void RemoveObserver(WindowTreeConnectionObserver* observer) override;
 
   // Overridden from WindowTreeClient:
   void OnEmbed(ConnectionSpecificId connection_id,
                mojom::WindowDataPtr root,
                mojom::WindowTreePtr tree,
                Id focused_window_id,
                uint32_t access_policy) override;
   void OnEmbeddedAppDisconnected(Id window_id) override;
   void OnUnembed() override;
   void OnWindowBoundsChanged(Id window_id,
@@ skipping 62 matching lines @@
   mojo::Binding<WindowTreeClient> binding_;
   mojom::WindowTreePtr tree_ptr_;
   // Typically this is the value contained in |tree_ptr_|, but tests may
   // directly set this.
   mojom::WindowTree* tree_;
 
   bool is_embed_root_;
 
   bool in_destructor_;
 
+  base::ObserverList<WindowTreeConnectionObserver> observers_;
+
   MOJO_DISALLOW_COPY_AND_ASSIGN(WindowTreeClientImpl);
 };
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_PUBLIC_CPP_LIB_WINDOW_TREE_CLIENT_IMPL_H_