fail on bad size or firstHeapAllocation creating GrSubRunAllocator

Double check sizes coming into sub run allocator.

Bug: oss-fuzz:45638

Change-Id: Ice9ab49dc0af789bf59efde270024321c5cf0f28
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/521836
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed