GitLab

Set the discardable memory allocator before fuzzing to avoid spurious
null derefs when discardable memory is allocated.
Also, move fuzzer build config to
//skia/tools/fuzzers/BUILD.gn

Bug: 903632, 904613
Change-Id: Ib987333706309eb470bcb988c53ddeebf5f5851e
Reviewed-on: https://chromium-review.googlesource.com/c/1336430
Commit-Queue: Jonathan Metzman <metzman@chromium.org>
Reviewed-by: Leon Scroggins <scroggo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609339}