Vulkan: Don't finish on swap. This will enable the next frame to render while the previous frame's command buffers are executing and rendering is happening. This should speed up the Vulkan perf test. BUG=angleproject:1898 Change-Id: I0820300d7934ef280cf75628239fe40dc96b8242 Reviewed-on: https://chromium-review.googlesource.com/445799 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>