Tagging with blocker label, please undo if not the case.

This behaviour follows from this markup in chrome/browser/resources/feedback/html/default.html:

<!-- Screenshot -->
<div id="screenshot-container" class="checkbox-field-container">
  <input id="screenshot-checkbox" type="checkbox" aria-labelledby="screenshot-label">
  <label id="screenshot-label" i18n-content="screenshot"></label>
  <img id="screenshot-image" alt="screenshot">
</div>

Because <img id="screenshot-image" alt="screenshot"> has no src set the image now 'represents some text' in the language of the spec (1) and so we now display the optional broken image icon that the spec permits/suggests (2). Later the src does get set by some js and the image loads, but until that happens a broken image icon will be displayed along with the alt text.

(1) https://html.spec.whatwg.org/multipage/embedded-content.html#the-img-element
(2) https://html.spec.whatwg.org/multipage/rendering.html#images-3https://html.spec.whatwg.org/multipage/rendering.html#images-3

Removing the alt text will let us treat the image as representing nothing and no broken image icon will be displayed. As this is an internal Chrome feature, rather than one exposed in Chromium, I don't think I can change it.

cc'ing in the owners of the affected file.

I think it's ok to remove the alt text. How that will affect screen readers?

You could add the alt text the same time you add the src. That would avoid displaying anything while you wait for the src to get set.

SGTM.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6f4d6990290d7a93807ea92e1112fceb5cb4dda6

commit 6f4d6990290d7a93807ea92e1112fceb5cb4dda6
Author: Ahmed Fakhry <afakhry@google.com>
Date: Thu Oct 19 16:02:36 2017

Feedback: Fix the broken image screenshot

The spec suggests showing a broken image icon when and <img> element
has an alt text attribute but no src attribute. To avoid this, we
set the alt text only when we set the src of the img element.

BUG= 773985 
TEST=manual

Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I3884e736a8a7b0e3fa40ea483882d20916a81a00
Reviewed-on: https://chromium-review.googlesource.com/727107
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510098}
[modify] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/chrome/browser/resources/feedback/html/default.html
[modify] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/chrome/browser/resources/feedback/js/feedback.js

Your change meets the bar and is auto-approved for M63. Please go ahead and merge the CL to branch 3239 manually. Please contact milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), gkihumba@(ChromeOS), govind@(Desktop)

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

Please merge your change to M63 branch 3239 by 4:00 PM PT today, Friday so we can take it in for next M63 dev release. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a8dd02d1d6de9e7c3606a1b6148c9780bdd638fd

commit a8dd02d1d6de9e7c3606a1b6148c9780bdd638fd
Author: Ahmed Fakhry <afakhry@google.com>
Date: Fri Oct 20 17:07:43 2017

[Merge to M63] Feedback: Fix the broken image screenshot

The spec suggests showing a broken image icon when and <img> element
has an alt text attribute but no src attribute. To avoid this, we
set the alt text only when we set the src of the img element.

TBR=xiyuan@chromium.org
BUG= 773985 
TEST=manual

(cherry picked from commit 6f4d6990290d7a93807ea92e1112fceb5cb4dda6)

Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I3884e736a8a7b0e3fa40ea483882d20916a81a00
Reviewed-on: https://chromium-review.googlesource.com/727107
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#510098}
Reviewed-on: https://chromium-review.googlesource.com/731040
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/branch-heads/3239@{#112}
Cr-Branched-From: adb61db19020ed8ecee5e91b1a0ea4c924ae2988-refs/heads/master@{#508578}
[modify] https://crrev.com/a8dd02d1d6de9e7c3606a1b6148c9780bdd638fd/chrome/browser/resources/feedback/html/default.html
[modify] https://crrev.com/a8dd02d1d6de9e7c3606a1b6148c9780bdd638fd/chrome/browser/resources/feedback/js/feedback.js

Retested above issue on Windows (7,8,8.1,10), Linux (14.04 LTS) and Mac 10.12.6) OS using latest canary #64.0.3247.0 build and issue seems fixed hence adding TE-Verified labels.

Deleted: Fixed Video.mov 3.1 MB

Fixed Video.mov 3.1 MB Download

Retested above issue on Windows (7,8,8.1,10), Linux (14.04 LTS) and Mac (10.12.6) OS using Dev 63.0.3239.16 build and issue seems fixed hence adding TE-Verified labels.

Deleted: Fixed Video.mov 2.8 MB

Fixed Video.mov 2.8 MB Download