Minor fixes for buffet build

Certain toolchains compile headers independently, and thus noticed some
missing #includes. This also removes the default_malloc_impl module,
as that gives linking errors in some environments because a symbol
is potentially missing depending on link order.

See also http://cl/572301023

Bug: b/40045064
Bug: b/237076898
Change-Id: Ia0a3f32bdab9bc92d09eddd3e5dc7c190cb5caf3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/765357
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
20 files changed