Add GrThreadSafePipelineBuilder

GrThreadSafePipelineBuilder is the generic, base object the
GrContextThreadSafeProxy will hold. Each backend will create a
backend-specific version that is shared between the direct context
and the (possibly many) utility contexts.

Right now GrThreadSafePipelineBuilder just holds the pipeline
creation stats. Relatedly only GrGLGpu::ProgramCache and
GrVkResourceProvider::PipelineStateCache currently derive from
the new class (since they are the only backends that generate
pipeline stats).

Change-Id: I58f441c5c2b870bb5970c29cba19d1775864d52e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/378320
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
30 files changed