Clarify how the `analyze` step should work in MB (and elsewhere).

(This is just a doc/spec change. Actual code changes to implement
this will follow).

[email protected], [email protected]
BUG=552146

Review URL: https://codereview.chromium.org/1412733015

Cr-Commit-Position: refs/heads/master@{#359403}
2 files changed