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This will need a recipe-side change to pass the paths known to recipe
(from the path recipe module) and properties (from the properties
recipe module).

Each of these key-value pairs is passed as two command line arguments,
so that parsing them is easy and rock solid (avoids escaping issues),
and is also easy to convert to dict python-side.

BUG=422235
R=iannucci@chromium.org

Review URL: https://codereview.chromium.org/649683005

Cr-Commit-Position: refs/heads/master@{#300659}