Trace function return values after function-exit.

This will allow function return values to be easily seen when stepping
"over." This has the unexpected side benefit of generating slightly
fewer ops when a function has unoptimizable conditional returns.

Change-Id: I48d23de635d3caaddff91aa595593d0371dfcdcb
Bug: skia:12708
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/481076
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
6 files changed