Animate the fullscreen exit bubble's opacity instead of its bounds when in immersive fullscreen

chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc

Index: chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc
diff --git a/chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc b/chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc
index 612c036869969948c29b0d95c7584a241624405c..120750e4d48e3b7f207cec51987d3880f455619f 100644
--- a/chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc
+++ b/chrome/browser/ui/gtk/fullscreen_exit_bubble_gtk.cc
@@ -225,6 +225,10 @@ bool FullscreenExitBubbleGtk::IsAnimating() {
   return slide_widget_->IsAnimating();
 }
 
+bool FullscreenExitBubbleGtk::CanMouseTriggerSlideIn() const {
+  return true;
+}
+
 void FullscreenExitBubbleGtk::StartWatchingMouseIfNecessary() {
   if (!fullscreen_bubble::ShowButtonsForType(bubble_type_))
     StartWatchingMouse();