Faster, thread-safe implementation

Bug: skia:
Change-Id: I401c5a9885c348aa424ab07b094acecddb209490
Reviewed-on: https://skia-review.googlesource.com/25860
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
7 files changed