mus Window Server: implement event capture

components/mus/ws/event_dispatcher_delegate.h

 // Copyright 2015 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_WS_EVENT_DISPATCHER_DELEGATE_H_
 #define COMPONENTS_MUS_WS_EVENT_DISPATCHER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include "components/mus/public/interfaces/input_events.mojom.h"
 
 namespace mus {
 namespace ws {
 
 class ServerWindow;
 
 // Used by EventDispatcher for mocking in tests.
 class EventDispatcherDelegate {
  public:
   virtual void OnAccelerator(uint32_t accelerator, mojom::EventPtr event) = 0;
 
   virtual void SetFocusedWindowFromEventDispatcher(ServerWindow* window) = 0;
   virtual ServerWindow* GetFocusedWindowForEventDispatcher() = 0;
 
+  virtual void SetCapture(ServerWindow* window) = 0;

[sky, 2016/02/10 17:38:22]

Clarify when these are called. In particular it's not clear when ReleaseCapture
vs OnLostCapture is called.
Also, I wouldn't supply a window to SetCapture/ReleaseCapture unless you need
it. It helps clarify this is intended to set/release capture on the native
display. In fact maybe the two should be called
SetNativeCapture/ReleaseNativeCapture.

[jonross, 2016/02/10 19:45:49]

Done.

As discussed offline the two OnLostCapture methods have been renamed to make
them more clear as to their functionality

+  virtual void ReleaseCapture(ServerWindow* window) = 0;
+  virtual void OnLostCapture(ServerWindow* window) = 0;
+
   // |in_nonclient_area| is true if the event occurred in the non-client area.
   virtual void DispatchInputEventToWindow(ServerWindow* target,
                                           bool in_nonclient_area,
                                           mojom::EventPtr event) = 0;
 
  protected:
   virtual ~EventDispatcherDelegate() {}
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_EVENT_DISPATCHER_DELEGATE_H_