Reduce delay to unpause occlusion tracker after overview mode ends

This patch is a temporary fix to reduce the delay before occlusion
tracker is unpaused after overview mode is dismissed. It is a temporary
fix to load web contents immediately instead of waiting on the occlusion
tracker for 5 seconds.

Bug: 904617
Change-Id: Ib1d4957638965fd34ffa719c057d234a058d7e08
Component: Window selector controller
Reviewed-on: https://chromium-review.googlesource.com/c/1332778Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Malay Keshav <malaykeshav@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607409}

ash/wm/overview/window_selector_controller.cc

@@ -49,7 +49,7 @@ constexpr int kOcclusionPauseDurationForStartMs = 50;
 
 // Wait longer when exiting overview mode in case when a user
 // may re-enter overview mode immediately, contents are ready.
-constexpr int kOcclusionPauseDurationForEndMs = 5000;
+constexpr int kOcclusionPauseDurationForEndMs = 500;
 
 // Returns true if |window| should be hidden when entering overview.
 bool ShouldHideWindowInOverview(const aura::Window* window) {