Don't calculate native window occlusion with headless.

headless_browser_tests fail with native window occlusion turned on.
Specifically, headless browser tests have |root_window_hwnd| of 0, which
causes a DCHECK when the tracking is disabled for the window.

This is in preparation for enabling native window occlusion by default.

Bug: 813093
Change-Id: I525f8f1c1572654bc5e5ea25dca385d3d7c48fb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1815609Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: David Bienvenu <davidbienvenu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698636}

ui/aura/window_tree_host.cc

@@ -38,6 +38,7 @@
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/icc_profile.h"
+#include "ui/gfx/switches.h"
 #include "ui/platform_window/platform_window_init_properties.h"
 
 #if defined(OS_WIN)
@@ -81,7 +82,9 @@ class ScopedLocalSurfaceIdValidator {
 
 #if defined(OS_WIN)
 bool IsNativeWindowOcclusionEnabled() {
-  return base::FeatureList::IsEnabled(features::kCalculateNativeWinOcclusion);
+  return !base::CommandLine::ForCurrentProcess()->HasSwitch(
+             switches::kHeadless) &&
+         base::FeatureList::IsEnabled(features::kCalculateNativeWinOcclusion);
 }
 #endif  // OS_WIN