The omnibox close button is down below the keyboard, quite low in the scene.  When flat in the XY plane it looks weird, especially on hover, when it moves forward, and the user has a top-down view of the movement.

UX indicated that buttons like this should generally directly face the user, instead.  This was done for the omnibox button.

We should apply the same rotation to the voice input cancel button, fullscreen exit button, and possibly any other prompt-cancelling round button.