Handle touches on the bubble bar in Overview

If the bubble bar is visible and we're in Overview, set the touchable region
of the Taskbar to include the bubble bar bounds.

Fixes: 290197298
Test: Manual
      - Add multiple bubbles to the bubble bar
      - Go to Overview
      - Tap on the bubble bar
      -- Observe that the bubble bar expands
      - Tap on different bubbles
      -- Observe that the bubble bar updates correctly
      - Tap outside the bubble bar
      -- Observe that the bubble bar collapses
      - Tap outside of the bubble bar again
      -- Observe that the launcher state changed and we are in Home
Change-Id: I722778ee41b50ebca57431bb303da89104d25090