HeadsUp: Respect system decorations when adding view.

    - FLAG_LAYOUT_IN_SCREEN ignores system decorations, so
    a heads up view in landscape would end up underneath the navbar

    - FLAG_LAYOUT_NO_LIMITS allows the window to exceed the screen
    limits all together

      Removing both these flags makes Heads Up respect both system
    decorations and the screen limits.

Change-Id: I6f111e1c5701d493979be0cb596f11bc1b437fda
SystemUI: Improve HeadsUp expanding performance.

Change-Id: Ifd31caca6d2eb2432772b6a63f6b545f8288f449