Extract touchscreen device management into a generic manager

ash/test/ash_test_helper_unittest.cc

Index: ash/test/ash_test_helper_unittest.cc
diff --git a/ash/test/ash_test_helper_unittest.cc b/ash/test/ash_test_helper_unittest.cc
index f5eae6006b93d9cbdde5b5dd5bd32277e881e864..8273af8637d8f7671274f7ef7b811923076f6a98 100644
--- a/ash/test/ash_test_helper_unittest.cc
+++ b/ash/test/ash_test_helper_unittest.cc
@@ -4,6 +4,7 @@
 
 #include "ash/test/ash_test_helper.h"
 
+#include "base/at_exit.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/views/widget/widget.h"
@@ -35,6 +36,7 @@ class AshTestHelperTest : public testing::Test {
   }
 
  private:
+  base::ShadowingAtExitManager at_exit_;
   base::MessageLoopForUI message_loop_;
   scoped_ptr<ash::test::AshTestHelper> ash_test_helper_;