This reverts commit c3d1208d.

Also:
* Instead of replacing "manifest", just add a new "source_manifest" 
to the output JSON.  This allow transition without breakage.
* Change the test api so test for recipe output changes.

The plan is to land this first, switch all downstream to "source_manifest",
and then remove the original "manifest" key.

Bug: 772529,776299
Change-Id: Iffb75f18046f8e4c058afe077872d4257b9dd754
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: skiabuildbot
Recipe-Nontrivial-Roll: release_scripts
Recipe-Nontrivial-Roll: skia
Recipe-Nontrivial-Roll: skiabuildbot
Recipe-Nontrivial-Roll: build
Reviewed-on: https://chromium-review.googlesource.com/731378Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>