I don't have convenient access to a USB -> display adapter right now.

Ahmed or Malay, can you build with use_vulcanize = false (in args.gn) and break on exceptions to see if you can identify the root cause? Or just click on the {} ('pretty print') icon at the bottom-left of the source view for crisper.js and debug from there.

It's all because this.$.slider.immediateValue for this USB display is NaN. I think because this monitor only supports a single resolution. I fixed the issue by using this.$.slider.value instead of this.$.slider.immediateValue here: https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/controls/settings_slider.js?q=findNearestIndex+package:%5Echromium$&l=55

Here's some analysis:

with use_vulcanize=false: we hit it from two paths:

1 --------------------------------------------------------------------
Uncaught Error: Assertion failed
    at assert (util.js:27) 
    at HTMLElement.findNearestIndex_ (settings_slider.js:132)
    at HTMLElement.valueChanged_ (settings_slider.js:107)
    at HTMLElement._complexObserverEffect (polymer-extracted.js:1656)
    at HTMLElement._complexObserverPathEffect (polymer-extracted.js:2266)
    at HTMLElement._pathEffector (polymer-extracted.js:2245)
    at HTMLElement._notifyPath (polymer-extracted.js:2146)
    at HTMLElement.set (polymer-extracted.js:2205)
    at HTMLElement.onSliderChanged_ (settings_slider.js:59)
    at HTMLElement.handler (polymer-extracted.js:550)

2 --------------------------------------------------------------------
Uncaught Error: Assertion failed
    at assert (util.js:27)
    at HTMLElement.findNearestIndex_ (settings_slider.js:formatted:131)
    at HTMLElement.valueChanged_ (settings_slider.js:formatted:107)
    at HTMLElement._complexObserverEffect (polymer-extracted.js:1656)
    at HTMLElement._effectEffects (polymer-extracted.js:1491)
    at HTMLElement._propertySetter (polymer-extracted.js:1475)
    at HTMLElement.__setProperty (polymer-extracted.js:1484)
    at HTMLElement._applyEffectValue (polymer-extracted.js:1967)
    at HTMLElement._annotationEffect (polymer-extracted.js:1630)
    at HTMLElement._effectEffects (polymer-extracted.js:1491)


It's hitting this assert: https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/controls/settings_slider.js?q=findNearestIndex+package:%5Echromium$&l=132

The value of |this.pref.value| that we send to this function is undefined: https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/controls/settings_slider.js?q=findNearestIndex+package:%5Echromium$&l=109

OK. It's unexpected that immediateValue is NaN, but we can test for that and use this.value instead. Could you put up a CL with that change (since you can test it) and make me the reviewer? Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/77ac96ae13745efb0300a75232dca1251cd5ada2

commit 77ac96ae13745efb0300a75232dca1251cd5ada2
Author: afakhry <afakhry@chromium.org>
Date: Wed Apr 19 23:33:15 2017

Fix MD display settings when the display supports a single resolution

Use this.$.slider.value instead of this.$slider.immediateValue when
this.$.slider.immediateValue is invalid.

BUG= 712842 
TEST=manually by connected an MIMO external USB display.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2829663004
Cr-Commit-Position: refs/heads/master@{#465807}

[modify] https://crrev.com/77ac96ae13745efb0300a75232dca1251cd5ada2/chrome/browser/resources/settings/controls/settings_slider.js

Your change meets the bar and is auto-approved for M59. Please go ahead and merge the CL to branch 3071 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), gkihumba@(ChromeOS), Abdul Syed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee13d6d2a7d3ca2b27c897a1567d915f2cf900f6

commit ee13d6d2a7d3ca2b27c897a1567d915f2cf900f6
Author: Ahmed Fakhry <afakhry@google.com>
Date: Fri Apr 21 00:03:57 2017

[Merge to M59] Fix MD display settings when the display supports a single resolution

Use this.$.slider.value instead of this.$slider.immediateValue when
this.$.slider.immediateValue is invalid.

TBR=stevenjb@chromium.org
BUG= 712842 
TEST=manually by connected an MIMO external USB display.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2829663004
Cr-Commit-Position: refs/heads/master@{#465807}
(cherry picked from commit 77ac96ae13745efb0300a75232dca1251cd5ada2)

Review-Url: https://codereview.chromium.org/2832953002 .
Cr-Commit-Position: refs/branch-heads/3071@{#106}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}

[modify] https://crrev.com/ee13d6d2a7d3ca2b27c897a1567d915f2cf900f6/chrome/browser/resources/settings/controls/settings_slider.js