Added a UI for the Interests Prototype.

It is added as a third (middle) option to the new tab page. When an interest
is clicked, the user is taken to a news search.

This is a continuation of .

To get this to work, use the flags:
--enable-ntp-interests --interests-url=http://localhost:8788/v1/interests
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Cr-Commit-Position: refs/heads/master@{#365264}
18 files changed