Perform ScopedPause in ShellSurfaceBase::OnSurfaceCommit

This fixes the case where the occlusion is changed while we are updating all the
pending properties. This caused some wrong occlusion updates.

Bug: 140563748
Test: Spurious occlusion update no longer occurs when leaving PIP.
Change-Id: Ic9bdbf62c655285eb8fbe1c80d221ff95bbbd096
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1794526
Commit-Queue: Stefan Kuhne <skuhne@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695323}

components/exo/shell_surface_base.cc

@@ -36,6 +36,7 @@
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_observer.h"
+#include "ui/aura/window_occlusion_tracker.h"
 #include "ui/aura/window_targeter.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/accelerators/accelerator.h"
@@ -521,6 +522,9 @@ ShellSurfaceBase::AsTracedValue() const {
 // SurfaceDelegate overrides:
 
 void ShellSurfaceBase::OnSurfaceCommit() {
+  // Pause occlusion tracking since we will update a bunch of window properties.
+  aura::WindowOcclusionTracker::ScopedPause pause_occlusion;
+
   // SetShadowBounds requires synchronizing shadow bounds with the next frame,
   // so submit the next frame to a new surface and let the host window use the
   // new surface.