Particles + Interpreter: Bind particle's SkRandom to "rand"

Update sample effects to use that (and remove the need for the
hacky workaround "random -> frame" affector I was using).

Current perf on my workstation, 6k particles updating:
native: 0.67 ms
interp: 0.97 ms

Change-Id: I3a2168c210d7431ffffe2b87ab6adade69f1dce7
Reviewed-by: Ethan Nicholas <>
Commit-Queue: Brian Osman <>
2 files changed