[Feed Internals] Add current content

This internals page is used to surface debugging information useful to
developers of the NTP Interest Feed. This CL surfaces the current
Feed content, including suggestion titles, URLs and other metadata.

https://screenshot.googleplex.com/gGGcX0BZkYM

Bug: 913126
Change-Id: I48dd63698229f43bb1671a0035e7c0b6cf34559a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1506539
Commit-Queue: Natalie Chouinard <chouinard@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Reviewed-by: Brandon Wylie <wylieb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638700}
7 files changed