Introduce aura::Env controller to abstract away changes to aura::Env

ui/aura/window_event_dispatcher.h

Index: ui/aura/window_event_dispatcher.h
diff --git a/ui/aura/window_event_dispatcher.h b/ui/aura/window_event_dispatcher.h
index d54d10a3a8325fc71e3788ca9f0b8c349a37f3a9..59f7b4f0cf64fb161d578925b9d8aa3b02bba56f 100644
--- a/ui/aura/window_event_dispatcher.h
+++ b/ui/aura/window_event_dispatcher.h
@@ -5,8 +5,6 @@
 #ifndef UI_AURA_WINDOW_EVENT_DISPATCHER_H_
 #define UI_AURA_WINDOW_EVENT_DISPATCHER_H_
 
-#include <stdint.h>
-
 #include <memory>
 #include <vector>
 
@@ -45,6 +43,7 @@ class TouchEvent;
 
 namespace aura {
 class TestScreen;
+class EnvInputStateController;
 class WindowTargeter;
 class WindowTreeHost;
 
@@ -246,9 +245,6 @@ class AURA_EXPORT WindowEventDispatcher : public ui::EventProcessor,
 
   WindowTreeHost* host_;
 
-  // Touch ids that are currently down.
-  uint32_t touch_ids_down_;
-
   Window* mouse_pressed_handler_;
   Window* mouse_moved_handler_;
   Window* event_dispatch_target_;
@@ -272,6 +268,8 @@ class AURA_EXPORT WindowEventDispatcher : public ui::EventProcessor,
 
   bool transform_events_;
 
+  std::unique_ptr<EnvInputStateController> env_controller_;
+
   // Used to schedule reposting an event.
   base::WeakPtrFactory<WindowEventDispatcher> repost_event_factory_;