Add surface view to IME

Applications that choose to hide the content area and draw their own view will use this surface area to draw on.

Fix: 171056783
Bug: 162268101
Bug: 170343703
Test: Manual
Change-Id: Ia6899bbe54773ae3752131dd662508bfe69c9a0e
Merged-In: Ia6899bbe54773ae3752131dd662508bfe69c9a0e
16 files changed