Make aura_demo work on Mac

ui/aura/env.cc

Index: ui/aura/env.cc
diff --git a/ui/aura/env.cc b/ui/aura/env.cc
index 0982d91ad265ca72a887bf2065eb7c1a3ba932be..0bd69326f6695944ab9659f6187e2fbb18b6b6a2 100644
--- a/ui/aura/env.cc
+++ b/ui/aura/env.cc
@@ -5,6 +5,7 @@
 #include "ui/aura/env.h"
 
 #include "base/command_line.h"
+#include "base/message_loop/message_pump_dispatcher.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/input_state_lookup.h"
 #include "ui/aura/window.h"
@@ -75,8 +76,7 @@ bool Env::IsMouseButtonDown() const {
       mouse_button_flags_ != 0;
 }
 
-#if !defined(OS_MACOSX) && !defined(OS_ANDROID) && \
-    !defined(USE_GTK_MESSAGE_PUMP)
+#if defined(USE_AURA)
 base::MessageLoop::Dispatcher* Env::GetDispatcher() {
 #if defined(USE_X11)
   return base::MessagePumpX11::Current();