Merge Vulkan Compute work into master.

Bug: skia:
Change-Id: I37ee0c30620bd998586a22f5d6e8177ebcecb178
Reviewed-on: https://skia-review.googlesource.com/147083
Reviewed-by: Allan MacKinnon <allanmac@google.com>
Commit-Queue: Allan MacKinnon <allanmac@google.com>
Auto-Submit: Allan MacKinnon <allanmac@google.com>
251 files changed