Refactor graphics environment initialization

Put all of the setupGraphicsSupport-related code into one function so
its easier to follow the full logic, and less intrusive to the code
around the call-site. This isn't supposed to change behavior at all,
but is preparation for the next change which will.

Bug: 38215658
Test: launch Clock, observe relevant events in systrace
Change-Id: I157b6233c0e9daf65e41697b504aa7e7d684401c