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Not done in this CL, but intended in the future:
* Genre should be able to store multiple values.
* TV episode images.
* Play next episode.
* Storage of the media feed items in media history.
* End to end testing using a full JSON example.

Change-Id: Ib4c6d9421c61ed98426aabc5b6056f0437195782
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2112957Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Sam Bowen <sgbowen@google.com>
Cr-Commit-Position: refs/heads/master@{#756355}