fix: delay handling occlusion events to avoid flicker on macOS (#18661)

* chore: add debounce on the updateWebContentsVisibility method to ensure quick changes in occlusion do not result in flickering

* chore: update old patch headers

patches/chromium/.patches

@@ -77,3 +77,4 @@ frame_host_manager.patch
 cross_site_document_resource_handler.patch
 woa_compiler_workaround.patch
 crashpad_pid_check.patch
+chore_add_debounce_on_the_updatewebcontentsvisibility_method_to.patch

patches/chromium/chore_add_debounce_on_the_updatewebcontentsvisibility_method_to.patch

@@ -0,0 +1,65 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Samuel Attard <sattard@slack-corp.com>
+Date: Wed, 5 Jun 2019 15:11:00 -0700
+Subject: chore: add debounce on the updateWebContentsVisibility method to
+ ensure quick changes in occlusion do not result in flickering
+
+diff --git a/content/app_shim_remote_cocoa/web_contents_view_cocoa.h b/content/app_shim_remote_cocoa/web_contents_view_cocoa.h
+index 230e259f6017310e556d11dec43973b74015f191..ebd19fc31efef50677da417dfd69f0c8cce6c682 100644
+--- a/content/app_shim_remote_cocoa/web_contents_view_cocoa.h
++++ b/content/app_shim_remote_cocoa/web_contents_view_cocoa.h
+@@ -58,6 +58,8 @@ CONTENT_EXPORT
+                        offset:(NSPoint)offset;
+ - (void)clearViewsHostableView;
+ - (void)updateWebContentsVisibility;
++- (remote_cocoa::mojom::Visibility)currentVisibility;
++- (void)notifyWebContentsVisibilityChanged;
+ - (void)viewDidBecomeFirstResponder:(NSNotification*)notification;
+ @end
+ 
+diff --git a/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm b/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
+index 615fe671d415747cb84f673327629d3dc771039e..6c31ba5b9149161784f5813598ddcf30e2d8af2a 100644
+--- a/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
++++ b/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
+@@ -257,9 +257,14 @@ - (void)viewDidBecomeFirstResponder:(NSNotification*)notification {
+   host_->OnBecameFirstResponder(direction);
+ }
+ 
+-- (void)updateWebContentsVisibility {
++- (void)notifyWebContentsVisibilityChanged {
+   if (!host_)
+     return;
++
++  host_->OnWindowVisibilityChanged([self currentVisibility]);
++}
++
++- (Visibility)currentVisibility {
+   Visibility visibility = Visibility::kVisible;
+   if ([self isHiddenOrHasHiddenAncestor] || ![self window])
+     visibility = Visibility::kHidden;
+@@ -267,7 +272,24 @@ - (void)updateWebContentsVisibility {
+     visibility = Visibility::kVisible;
+   else
+     visibility = Visibility::kOccluded;
+-  host_->OnWindowVisibilityChanged(visibility);
++  return visibility;
++}
++
++- (void)updateWebContentsVisibility {
++  if (!host_)
++    return;
++  // Cancel any pending notifications visibility changes, this ensures that the latest incoming change is the only
++  // change that will take affect
++  [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(notifyWebContentsVisibilityChanged) object:nil];
++
++  Visibility visibility = [self currentVisibility];
++
++  // If it's visible, notify immediately to render ASAP
++  if (visibility == Visibility::kVisible)
++    host_->OnWindowVisibilityChanged(visibility);
++  else
++    // If it's occluded queue it for 3 seconds to be sure that it isn't a double kOccluded -> kVisible
++    [self performSelector:@selector(notifyWebContentsVisibilityChanged) withObject:nil afterDelay:3.0];
+ }
+ 
+ - (void)resizeSubviewsWithOldSize:(NSSize)oldBoundsSize {