CCing huangs@ and mastiz@ who likely know best about future plans

I wrote the code but haven't touched it for ages. A potential application is in bookmarks and history -- but realistically nobody (including me) cares enough to push this forward. Also I'm not aware of any existing uses.

The icons also depend on dominant color extraction code that +rogerm@ wrote. I don't know the status of that code (Removable? Reusable elsewhere?) 

So I'm in favor of ripping this out. Let me know if you want any help.

It's not obvious to me whether it's dead code, in particular around https://cs.chromium.org/chromium/src/chrome/renderer/searchbox/searchbox.cc?l=69&rcl=db9cef9964f34067223f3d95f8a0206a3d07254b, but huangs' optimism suggests so.

If it is indeed dead, +1 to removing it. I'm not aware of future plans that would depend on it.

I wrote the CL with the line you cited in https://codereview.chromium.org/1017853002 .

We were going to replace NTP tiles (screenshots) with large icons, and if missing, render fallback with dominant color. The project got shelved for desktop, but got green light for Clank. Meanwhile, Clank uses its own Java fallback icon generator (RoundedIconGenerator), and doesn't use chrome://fallback-icon.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/59f676347cd7bb0ec16a9cae0e1257f6548dc3b4

commit 59f676347cd7bb0ec16a9cae0e1257f6548dc3b4
Author: pkotwicz <pkotwicz@chromium.org>
Date: Fri May 26 19:28:05 2017

Delete unused chrome://fallback-icon/ handling

BUG= 712475 
R=huangs,jkrcal,pkasting
TBR=treib for removal of stray includes in chrome/browser/search/

Review-Url: https://codereview.chromium.org/2883053003
Cr-Commit-Position: refs/heads/master@{#475087}

[modify] https://crrev.com/59f676347cd7bb0ec16a9cae0e1257f6548dc3b4/chrome/browser/BUILD.gn
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[delete] https://crrev.com/b7a527720b277b3ec4af030be6c32e288f0b18c6/components/favicon_base/fallback_icon_url_parser.cc
[delete] https://crrev.com/b7a527720b277b3ec4af030be6c32e288f0b18c6/components/favicon_base/fallback_icon_url_parser.h
[delete] https://crrev.com/b7a527720b277b3ec4af030be6c32e288f0b18c6/components/favicon_base/fallback_icon_url_parser_unittest.cc