Runtime effects: Detect passthrough sample calls automatically

As explained, this is *very* conservative. It only works when the child
is sampled from within main, and using a direct reference to the coords
parameter. If that parameter is ever modified (even after being used),
the optimization doesn't happen. For most cases, this is fine.

Bug: skia:11869
Change-Id: Ia06181730a6d07e2a4fe2de4cc8e8c3402f0dc52
Reviewed-by: Michael Ludwig <>
Reviewed-by: John Stiles <>
Commit-Queue: Brian Osman <>
8 files changed