Define a policy to control the desktop browser occlusion

The policy will allow enterprises who are concerned about
the effect of native window occlusion in their environment
to disable it easily.

Bug: 813093
Change-Id: Ifef8af79652aba4e1433cc5d41585be866296ba1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032000
Commit-Queue: David Bienvenu <davidbienvenu@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741175}

diff --git a/ui/aura/BUILD.gn b/ui/aura/BUILD.gn
index 5e6aca17..32758aa 100644
--- a/ui/aura/BUILD.gn
+++ b/ui/aura/BUILD.gn

@@ -77,6 +77,8 @@
     "input_state_lookup.cc",
     "input_state_lookup_win.cc",
     "layout_manager.cc",
+    "native_window_occlusion_tracker.cc",
+    "native_window_occlusion_tracker.h",
     "native_window_occlusion_tracker_win.cc",
     "native_window_occlusion_tracker_win.h",
     "null_window_targeter.cc",