Looks like the slider has:
aria-valuenow: "1"
aria-valuetext: "100% (default)"

So Chromevox is reading aria-valuenow aloud as well as aria-valuetext, which is why we hear "one". On these sliders, we map values to percentages, so 1 === 100%, and 1.5 === 150%, etc.

+dtseng, what would you recommend we do here? Should we map 100 === 100% instead? I might need to make some custom code in the slider in that case so that the pref still gets set properly.

For reference, display_size_slider is https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/device_page/display_size_slider.js?q=aria-valuenow+file:%5Esrc/chrome/browser/resources/settings/+package:%5Echromium$&dr=C&l=123.

It is up to the user agent how these attributes get processed. It has been suggested by some (e.g. FF) to render valuetext in place of (rather than in addition to) valuenow. I can do this in ChromeVox.

The output would be:
"100 default, min 20, max 100, volume"

with replacement.

I'll also move around the range output, so that we have:
"100 default, volume, min 20, max 100"

Unfortunately, there's no minvaluetext afaik.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/89cd4f1e9541a600fb3c58d3befd966890c34362

commit 89cd4f1e9541a600fb3c58d3befd966890c34362
Author: David Tseng <dtseng@chromium.org>
Date: Sat Jun 23 00:40:55 2018

Reorder and fine-tune range output (e.g. sliders)


Trim whitespace for input type="tel" This fixes custom text fields of type="tel" that insert whitespace as padding.

Bug:  854891 
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I44e152c9b7246fd5b2da701b218cf4a89a979139
Reviewed-on: https://chromium-review.googlesource.com/1112301
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569861}
[modify] https://crrev.com/89cd4f1e9541a600fb3c58d3befd966890c34362/chrome/browser/resources/chromeos/chromevox/cvox2/background/output.js
[modify] https://crrev.com/89cd4f1e9541a600fb3c58d3befd966890c34362/chrome/browser/resources/chromeos/chromevox/cvox2/background/output_test.extjs