MacViews: Fix gn check fail for mac_views_browser on Aura dependencies.

ui/views/widget/widget_unittest.cc

Index: ui/views/widget/widget_unittest.cc
diff --git a/ui/views/widget/widget_unittest.cc b/ui/views/widget/widget_unittest.cc
index b85e3fc89e28f568b55446491e621f247803026b..759e7ed04a84f89e9e468bc404573c64ef816c96 100644
--- a/ui/views/widget/widget_unittest.cc
+++ b/ui/views/widget/widget_unittest.cc
@@ -36,8 +36,8 @@
 #include "ui/views/window/native_frame_view.h"
 
 #if defined(OS_WIN)
-#include "ui/aura/window.h"
-#include "ui/aura/window_tree_host.h"
+#include "ui/aura/window.h"            // nogncheck
+#include "ui/aura/window_tree_host.h"  // nogncheck

[tapted, 2016/09/19 03:23:36]

So the "alternative" to // nogncheck is to move the code that requires these
headers into a separate file. We should investigate all the cases in this CL -
it might not make sense to do that in all cases, but widget_unittest is probably
a good place to try it out. For example, the tests here that rely on these aura
headers might:
 - belong instead in native_widget_aura_unittest.cc, OR
 - sill be widget tests, but aura-specific so belong in a new file like
widget_aura_unittest.cc, OR
 - need to be enabled on Mac but are missing the right abstraction (e.g. a
generic interface in widget_test.h [similar to IsNativeWindowVisible()] that is
implemented in widget_test_mac.mm and widget_test_aura.cc

 #include "ui/base/view_prop.h"
 #include "ui/base/win/window_event_target.h"
 #include "ui/views/win/hwnd_util.h"