Part 1.1: Is policy list subsumed under subsuming policy?

This is part of an experimental feature Embedding-CSP.

In particular this is the initial effort in implementing
*3.3. Is policy list subsumed under subsuming policy?

Given two CSPSources, we try to determine whether one is
subsumed under another. If not, return false.

BUG=647588

Review-Url: https://codereview.chromium.org/2442513004
Cr-Commit-Position: refs/heads/master@{#429872}
3 files changed