Always emit all FP child functions before emitCode

This hoists logic that was being done only for GrSkSLFP to the base
class, and avoids having to write these functions lazily on first-call.

To simplify things further, stop storing the names of child processor
functions in the parent. Simply have each processor store its *own*
name. This avoids storing empty strings for null children.

Change-Id: I53afbae6dc0986575e3e91aba5532a27f7ef25d4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/434466
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
6 files changed