Reorder GLSL output so that functions are emitted last.

The Inliner likes to move function bodies around; after inlining, code
can inadvertently move upwards, above ProgramElements that the code
relies on. We work around this by always emitting functions last.

Change-Id: Ie5486cc3a79a478920342fb9f578d575486fb4cf
Bug: skia:11186
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/354669
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
22 files changed