CL for pdf/ at https://chromium-review.googlesource.com/c/575388/.

@stevenjb, michaelpg: Can you share some instructions on how to trigger the to chromeos/ UIs that still reference iron-flex-layout.html (see 1st comment)?

network_ui.html is a debugging page found at chrome://network. For that one let's keep it readable, but don't worry too much about matching the existing format; it's developer UI.

I'm not familiar with arc_support; +khmel@

Easy way is using ARC Enabled devices. Login into Chrome. Open App Launcher and find Play Store icon. Clicking it would start ARC OptIn flow, which is based on chromeos/arc_support/main.html. Pass this flow and you should see several different pages, Terms shown, progress and so on.

Alternatively you may build Linux ChromeOS:
gn gen out/Debug --args='target_os="chromeos"  is_debug=true'
And run:
--user-data-dir=/tmp/chrome_temp_dir
 --login-manager --enable-arc 
Repeat steps above and you should see few pages: Terms loading, Terms page and error page that says that ARC cannot be started.

Thanks for the instructions.

Actually pdf/elements/viewer-pdf-toolbar/viewer-pdf-toolbar.html is not using the deprecated file, so no need to be migrated. Starting on the remaining ones.

I've updated everything (at https://chromium-review.googlesource.com/c/575388/) except for options_polymer.html, which per my understanding is triggered from the old Options code to display a component from the new MD Settings, see [1].

@stevenjb: Is there an easy way I can trigger this UI from a ChromeOS build on Linux?

[1] https://cs.chromium.org/chromium/src/chrome/browser/resources/options/chromeos/quick_unlock_configure_overlay.js?l=56

I think Dan ripped out some of the old options code so it's no longer fully functional? I think what's left is there because unraveling the cros login/oobe ui dependencies is complicated. I'm hoping to rip most of what's left out after we branch for 61.

In other words, if it's old options UI, I wouldn't worry about it. I don't see any references to that UI in login/oobe. (FWIW, the link to that was in the 'People' section, 'Manage screenlock', which does appear to still show an overlay if you want to see it. Don't use a Google account to test since it's disabled).

Thanks for the info. I was able to verify that an overlay is still shown from chrome://settings-frame, after removing the reference to the obsolete file.

Having said that, there are lots of (unrelated) errors in the console when the overlay shows up (verified they also happen on ToT), which supports the "no longer fully functional" comment above, see screenshot. 

Deleted: errors_tot.png 91.7 KB

	errors_tot.png 91.7 KB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a30b99442eda462ead04bf4a1d51f86b21a4b9bf

commit a30b99442eda462ead04bf4a1d51f86b21a4b9bf
Author: dpapad <dpapad@chromium.org>
Date: Tue Jul 18 20:19:57 2017

WebUI: Remove remaining usage of obsolete iron-flex-layout.html

Also remove the deprecated files from polymer_resources.grdp since
they are not needed anymore.

Bug:  744902 
Change-Id: I35ab3bbbb2e9d42758430672aba4736393e6056d
Reviewed-on: https://chromium-review.googlesource.com/575388
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487583}
[modify] https://crrev.com/a30b99442eda462ead04bf4a1d51f86b21a4b9bf/chrome/browser/resources/chromeos/arc_support/main.html
[modify] https://crrev.com/a30b99442eda462ead04bf4a1d51f86b21a4b9bf/chrome/browser/resources/chromeos/network_ui/network_ui.css
[modify] https://crrev.com/a30b99442eda462ead04bf4a1d51f86b21a4b9bf/chrome/browser/resources/chromeos/network_ui/network_ui.html
[modify] https://crrev.com/a30b99442eda462ead04bf4a1d51f86b21a4b9bf/chrome/browser/resources/options/options_polymer.html
[delete] https://crrev.com/15e81433def80cc7a11017d070fc6268630f2b11/third_party/polymer/v1_0/components-chromium/iron-flex-layout/classes/compiled_resources2.gyp
[delete] https://crrev.com/15e81433def80cc7a11017d070fc6268630f2b11/third_party/polymer/v1_0/components-chromium/iron-flex-layout/classes/iron-flex-layout-extracted.js
[delete] https://crrev.com/15e81433def80cc7a11017d070fc6268630f2b11/third_party/polymer/v1_0/components-chromium/iron-flex-layout/classes/iron-flex-layout.html
[delete] https://crrev.com/15e81433def80cc7a11017d070fc6268630f2b11/third_party/polymer/v1_0/components-chromium/iron-flex-layout/classes/iron-shadow-flex-layout-extracted.js
[delete] https://crrev.com/15e81433def80cc7a11017d070fc6268630f2b11/third_party/polymer/v1_0/components-chromium/iron-flex-layout/classes/iron-shadow-flex-layout.html
[modify] https://crrev.com/a30b99442eda462ead04bf4a1d51f86b21a4b9bf/ui/webui/resources/polymer_resources.grdp