aura-mus: create an interactive ui test for drag and drop.

ui/aura/env.h

 // Copyright (c) 2012 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 UI_AURA_ENV_H_
 #define UI_AURA_ENV_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 106 matching lines @@
 
   friend class test::EnvTestHelper;
   friend class MusMouseLocationUpdater;
   friend class Window;
   friend class WindowTreeHost;
 
   explicit Env(Mode mode);
 
   void Init();
 
+  // After calling this method, all OSExchangeDataProvider instances will be
+  // Mus instances. We can't do this work in Init(), because our mode may
+  // changed via the EnvTestHelper.
+  void EnableMusOSExchangeDataProvider();
+
   // Called by the Window when it is initialized. Notifies observers.
   void NotifyWindowInitialized(Window* window);
 
   // Called by the WindowTreeHost when it is initialized. Notifies observers.
   void NotifyHostInitialized(WindowTreeHost* host);
 
   // Invoked by WindowTreeHost when it is activated. Notifies observers.
   void NotifyHostActivated(WindowTreeHost* host);
 
   void OnActiveFocusClientWindowDestroying();
@@ skipping 15 matching lines @@
   base::ObserverList<EnvObserver> observers_;
 
   int mouse_button_flags_;
   // Location of last mouse event, in screen coordinates.
   mutable gfx::Point last_mouse_location_;
   bool is_touch_down_;
   bool get_last_mouse_location_from_mus_;
   // This may be set to true in tests to force using |last_mouse_location_|
   // rather than querying WindowTreeClient.
   bool always_use_last_mouse_location_ = false;
+  // Whether we set ourselves as the OSExchangeDataProviderFactory.
+  bool is_os_exchange_data_provider_factory_ = false;
 
   std::unique_ptr<InputStateLookup> input_state_lookup_;
   std::unique_ptr<ui::PlatformEventSource> event_source_;
 
   ui::ContextFactory* context_factory_;
   ui::ContextFactoryPrivate* context_factory_private_;
 
   Window* active_focus_client_root_ = nullptr;
   client::FocusClient* active_focus_client_ = nullptr;
   std::unique_ptr<ActiveFocusClientWindowObserver>
       active_focus_client_window_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(Env);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ENV_H_