When taskbar would be stashed in 3 button mode, hide icons instead

In 0 button mode, stashing morphs the icons into the home handle. In 3 button mode, that doesn't make sense, but we should still hide the icons (and just keep the 3 nav buttons). You still can't manually stash via long press in 3 button mode, but this will address other states where we automatically stash the taskbar when we want to hide the icons from users (e.g. when pinning an app).

Test: Pin an app from overview in 3 button mode, ensure the taskbar icons disappear until unpinning
Bug: 190192993
Change-Id: I499c59bd9d7871ff64696b67065cf9d4863222a5
1 file changed