(Sorry, input fail.)

Steps to reproduce:
1) Open Chrome
2) Immediately open chrome://suggestions

Result: The page fails to load with an ERR_INVALID_URL error (as if chrome://suggestions was not valid Web UI URL). Then at a later point it suddenly works.

Marc, that seems like a bug for you :)

Huh. That page is provided by SuggestionsSource, which on Android is instantiated by MostVisitedSites: https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/android/most_visited_sites.cc&l=194
Which in turn is instantiated with the first NewTabPage, which means soon, but apparently not soon enough.

Yeah, if I open chrome://suggestions without opening an NTP (for example, restarting Chrome with chrome://suggestions open), it wouldn't be registered.

Could we just add a WebUI for chrome://suggestions and register the source there?

A WebUIController, you mean? I suppose.. seems a bit pointless if all it does is register the source, but I guess that's the way it's done.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0c8e07604abddf7f02daee2ad48314e12f2688b2

commit 0c8e07604abddf7f02daee2ad48314e12f2688b2
Author: treib <treib@chromium.org>
Date: Tue Apr 19 13:03:45 2016

Create a WebUIController for chrome://suggestions

This ensures that the URLDataSource is properly registered at startup.

BUG= 597653 

Review URL: https://codereview.chromium.org/1887403002

Cr-Commit-Position: refs/heads/master@{#388197}

[modify] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/browser/android/ntp/most_visited_sites.cc
[modify] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/browser/search/instant_service.cc
[delete] https://crrev.com/c1d083e60687f5def2026671fda54873b07c424f/chrome/browser/search/suggestions/suggestions_source.h
[rename] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/browser/search/suggestions/suggestions_ui.cc
[add] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/browser/search/suggestions/suggestions_ui.h
[modify] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
[modify] https://crrev.com/0c8e07604abddf7f02daee2ad48314e12f2688b2/chrome/chrome_browser.gypi