aura: Introduce EventInjector.

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 96 matching lines @@
   ui::ContextFactoryPrivate* context_factory_private() {
     return context_factory_private_;
   }
 
   // See CreateInstance() for description.
   void SetWindowTreeClient(WindowTreeClient* window_tree_client);
   bool HasWindowTreeClient() const { return window_tree_client_ != nullptr; }
 
  private:
   friend class test::EnvTestHelper;
+  friend class EventInjector;
   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
@@ skipping 51 matching lines @@
 
   ui::ContextFactory* context_factory_;
   ui::ContextFactoryPrivate* context_factory_private_;
 
   DISALLOW_COPY_AND_ASSIGN(Env);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ENV_H_