mus: Add PointerWatcher for passively observing mouse and touch events

components/mus/public/cpp/window_tree_delegate.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_WINDOW_TREE_DELEGATE_H_
 #define COMPONENTS_MUS_PUBLIC_CPP_WINDOW_TREE_DELEGATE_H_
 
 #include <string>
 
 #include "components/mus/public/interfaces/window_tree.mojom.h"
 #include "services/shell/public/interfaces/interface_provider.mojom.h"
 
+namespace ui {
+class Event;
+}
+
 namespace mus {
 
 class Window;
 class WindowTreeConnection;
 
 // Interface implemented by an application using the window manager.
 //
 // WindowTreeConnection is deleted by any of the following:
 // . If all the roots of the connection are destroyed and the connection is
 //   configured to delete when there are no roots (the default). This happens
@@ skipping 17 matching lines @@
   // connection). Afer this call |root| is deleted. If |root| is the only root
   // and the connection is configured to delete when there are no roots (the
   // default), then after |root| is destroyed the connection is destroyed as
   // well.
   virtual void OnUnembed(Window* root);
 
   // Called from the destructor of WindowTreeConnection after all the Windows
   // have been destroyed. |connection| is no longer valid after this call.
   virtual void OnConnectionLost(WindowTreeConnection* connection) = 0;
 
+  // Called when the WindowTreeConnection receives an input event observed via
+  // SetEventObserver().
+  virtual void OnEventObserved(const ui::Event& event) = 0;
+
  protected:
   virtual ~WindowTreeDelegate() {}
 };
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_PUBLIC_CPP_WINDOW_TREE_DELEGATE_H_