moar static flags

Like any normal variable, flags can be made file-scoped static,
and like any normal variable, mostly they should be if they can.

This CL converts most flags to be static, if only so that the
ones that do cross files stand out more clearly, and so that
there's more examples of static flags through the codebase for
people to ape.

Change-Id: Ibb5ddd7aa09fce073d0996ac3ef0487b078b7d79
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/202800
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
30 files changed