Remove SK_ALLOW_STATIC_GLOBAL_INITIALIZERS from tests.

The tests themselves should run fine if no factories were actually
registered. This isolates the last uses of this flag to the gpu code
which is actually depending on it.

Change-Id: Ief9c01abfc37c4e071d946d70ef85f13f94ae0f6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/213301
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
4 files changed