Update MakeChildFP to allow processor hierarchies to be created.

Previously, MakeChildFP avoided infinite recursion by rejecting any FP
that took inputs. MakeChildFP now generates random inputs up to a
user-supplied tree depth.

The ProcessorOptimizationValidationTest test has been updated to
test up to a tree depth of 3. The ProcessorCloneTest has been left at
a tree depth of 1 due to a bug that only appears on Galaxy S20/Mali G77.
The Mali bug doesn't appear to be related to FP cloning, but probably
deserves further analysis. (It appears that on this device, these
processors hooked together in sequence render a tiny bit differently
each time: DitherEffect -> RectBlurEffect -> ImprovedPerlinNoise. By
visual inspection it looks like the dither varies on each draw.)

Change-Id: Ib8f619eb7a8a9c9254080303504c20065ff35453
Bug: skia:10384, skia:10595
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308556
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
5 files changed