This will help for the command graph refactor so we can set up the
command buffer barriers before we start the render pass for draw.

Bug: angleproject:3539
Bug: angleproject:4029
Change-Id: If5a55db6ac1e06609a3a1e2245d7ab351152886a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2028450Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>