Currently, FullscreenManager.isOverlayVideoMode() is used in ContextualSearchManager and chromeFullscreenManager.shouldShowNotificationToast(). It appears as though the intended usage of isOverlayVideoMode() is to determine whether or not there is a fullscreen video being displayed onscreen.
However, what the method actually does is return whether or not we are using a ContentVideoView. This means that, when a div containing a video player is fullscreened (rather than fullscreening the player itself), ContextualSearchManager and shouldShowNotificationToast might not behave in the expected way.

The introduction of AndroidOverlays as a replacement to ContentVideoView means that isOverlayVideoMode() would no longer be useful at all.

This bug's goal is to identify the original intended usage of isOverlayVideoMode and to replace it with a more reliable signal