FWIW, this is the case with the old Options too. I agree it should be fixed, but don't think it should be a blocker for  issue 671375 .

did you try about:inducebrowsercrashforrealz yet? ;)

Notes from some initial investigation.

1) We are using a settings-input element for the home button text input field [1], which does not seem to currently expose any way to do validation from the outside.
2) settings-input itself does "auto validation" based on a given pattern, which we do not actually use, since we don't pass any value for "patterns", see [2].
3) We would need to do async validation calling StartupUrlsPageBrowserProxy#validateStartupPage to achieve same behavior as the "on startup" section, see [3].
4) The UI needs to be adjusted to accommodate the space needed for the validation error, see attachment.

[1] https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/appearance_page/appearance_page.html?l=123
[2] https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/controls/settings_input.html?l=18,20
[3] https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/on_startup_page/startup_urls_page_browser_proxy.js?l=28

Deleted: home_page_validation.png 29.5 KB

	home_page_validation.png 29.5 KB View Download

nah, this is a desktop blocker

To add to the list of things that is wrong with this - 
5) the secondary-text UI currently say "www.example.com" when the input is actually empty, which is kind of misleading and makes me think my homepage is actually set to www.example.com
6) there's no confirmation button to let the user say "ok I'm choosing this as my homepage url!", instead it just saves on pressing enter or on blur. I could see if a user just types in the url and refresh or close the window thinking they saved it.

Deleted: Screen Shot 2017-03-16 at 2.34.38 PM.png 37.1 KB

	Screen Shot 2017-03-16 at 2.34.38 PM.png 37.1 KB View Download

scottchen@: see also

https://bugs.chromium.org/p/chromium/issues/detail?id=619774
https://bugs.chromium.org/p/chromium/issues/detail?id=698611

dpapad@ or scottchen@: who wants to fix this?

dbeam@ there's yet another one: https://bugs.chromium.org/p/chromium/issues/detail?id=619768&desc=2

In there, bettes@ says the secondary text should say "Custom" when the field is empty, but tbuckley said in  Issue 698611  that the text should say "New Tab page" until the user enters something in there. Which one do I go with?

scottchen@: this bug is about validating the startup URL.  if this affects visual presentation, that's fine, but it's not about the oddness of the placeholder in this UI.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2f7628484099e467516f27c8a6e9f056461c1aab

commit 2f7628484099e467516f27c8a6e9f056461c1aab
Author: scottchen <scottchen@chromium.org>
Date: Sat Mar 25 01:13:37 2017

MD Settings: validate home button url input.

This CL adds validation to the home url input, and shows error message when the input is an invalid url. This CL also removes some of settings-input's logic, since it is no longer being used by anything outside of appearance-page.

BUG= 681243 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2766093002
Cr-Commit-Position: refs/heads/master@{#459614}

[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/app/settings_strings.grdp
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/appearance_page/appearance_browser_proxy.js
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/appearance_page/appearance_page.html
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/appearance_page/appearance_page.js
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/controls/settings_input.html
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/controls/settings_input.js
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/resources/settings/search_engines_page/search_engine_dialog.html
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc
[modify] https://crrev.com/2f7628484099e467516f27c8a6e9f056461c1aab/chrome/test/data/webui/settings/appearance_page_test.js