PiP: Don't invoke double-tap gesture (maximize) if menu is showing.

If the menu is showing and populated with icons, the user intention is
more likely to interact with the menu. Prioritize on that and drop
gestures such as double-tap.

Bug: 185458696
Bug: 184789345
Test: Double-tap while menu is showing
Change-Id: Icac92ec8cafdcb2f3a11919a4c6a227bf85d446c