GitLab

Refactored the available_script filtering: we now express it as a precondition
on the ScriptStatus for the current script. I made this precondition a default
precondition only when there is no existing ScriptStatusMatch explicitly set,
so it is now possible to run a script twice.

Change-Id: I2ceb87f62b18dfdb455c9fff2f883000da918848
Bug: 806868
Reviewed-on: https://chromium-review.googlesource.com/1224553
Commit-Queue: Ernest Galbrun <galbrun@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594649}