base

Move the layout code out of RenderSessionImpl. [DO NOT MERGE]

Also, switch to using a RelativeLayout from a LinearLayout. The change
will help in future when enabling transparent status and nav bar.

Change-Id: Ie4db5d28313f1c5ef775603788598a56409f92c7
(cherry picked from commit b1484862e2367d87d3ccbd0fd0a6d2598ed5918a)