fail on bad size or firstHeapAllocation creating GrSubRunAllocator
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 <53965154ffeecc4a10886eab9259e95965f2979a@google.com>
Commit-Queue: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia