Remove all global mutexes

Remove the SkBaseMutex (and SkBaseSemaphore). This allows all the thread
annotation machinery to work.

Change-Id: I2da420ec3165ccbcd90c474c0b62bfef42df2a53
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/221340
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
16 files changed