Use parent frame to calculate wallpaper offset

Session#setWallpaperZoomOut may be called when display is rotated
(DisplayInfo is updated) but wallpaper window has stopped to update
frame (isVisibleRequested() of wallpaper window is false). In this
case, when the zoom request calls to WallpaperController#
updateWallpaperOffset, it calculates the offset with inconsistent
orientation that causes unexpected wallpaper shift.

Because wallpaper has no fit-insets, its parent frame should equal
to display size. The example of wallaper WindowFrame:
  containing=[0,0][1080,2160] parent=[0,0][1080,2160]
  display=[-10000,-10000][10000,10000] mFrame=[0,0][1763,2160]
So use the parent frame to ensure that the offset is computed from
the frames with the same orientation.

Bug: 183181781
Test: WallpaperControllerTests

Change-Id: Icf55e3570c260b963fab6dc85814f9e8e305163c