This is similar to what we were discussing earlier this week with @dschuyler (and others), about not allowing dynamic content to show when first landing on chrome://settings. Similar argument can be made for the "Internet" section on CrOS, and creates problems when trying to scroll to a certain section programmatically.

We should consider moving the list of pages into a subpage. @bettes, what do you think?

There should be a cap on the list per  crbug.com/603305 . 

The subpage isn't necessary since since we've learned that the 95% of users have <3 sites for OnStartup. 


Re: removing dynamic content
I'm not opposed to considering this section to a subpage IF we begin to remove other inline dynamic content like WiFI. However, until we invest in that undertaking, I don't think this is worth fixing. 

Moving it to a subpage will also help by addressing an issue we're having with scrolling iron-lists that show limited entries. Given that this helps in multiple ways and there are no current pri-1 bugs, I'll look into moving this to a subpage.

Prototype screen shots. Alan, wdyt?

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fyi to stevenjb@

If we were to make this change, what if we made this a single line item instead, similar to, e.g. Sync where we show the setting value at the top level but only expose the control UI in the subpage?

While on the one hand the existing UI may "work" since we limit the number of pages we show, it has been the cause of more than its fair share of regressions due to the complexities of an expanding scrolling list embedded in a larger scrolling page, so I would also like to see the list moved to a subpage.

re #8 Moving the radio buttons to the subpage might look something like this.

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Alan, do you prefer #6 or #9?

I'll go with #9 for the time being so that you/we can try it out and live with it for a bit. There's time to change it before the branch if desired.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b1b6f101f5078d42160af02e26bd5c3c27a03100

commit b1b6f101f5078d42160af02e26bd5c3c27a03100
Author: Dave Schuyler <dschuyler@chromium.org>
Date: Sat Jul 08 02:20:36 2017

[MD settings] startup url list to a subpage

This CL moves the on startup settings off of the main settings page and
into a subpage.

Bug:  653376 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I46dd91fbd3e1bc4b28b6465ad0a3a08b7bee1927
Reviewed-on: https://chromium-review.googlesource.com/557971
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Dave Schuyler <dschuyler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485130}
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/app/settings_strings.grdp
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/on_startup_page/compiled_resources2.gyp
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/on_startup_page/on_startup_page.html
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/on_startup_page/on_startup_page.js
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/on_startup_page/startup_urls_page.html
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/on_startup_page/startup_urls_page.js
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/resources/settings/route.js
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/test/data/webui/settings/on_startup_browsertest.js
[modify] https://crrev.com/b1b6f101f5078d42160af02e26bd5c3c27a03100/chrome/test/data/webui/settings/startup_urls_page_test.js

Alan, feel free to make further bugs for other changes in this UI as desired.