Add ability to pre-initialize vulkan semaphores when flushing surfaces

Bug: skia:
Change-Id: I2d3eb68d2ac6045fe3e30350fdd21140e22861d7
Reviewed-on: https://skia-review.googlesource.com/24645
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
5 files changed