Reproduces in 67.0.3396.99 on Google Eve

This wouldn't be considered a regression since it was assumed to have never worked. 

There is no difference if braille mode is enabled or disabled, if screen magnifier support is enabled or disabled. 

I actually find that Chromevox has the same bug (you can turn on chromevox after opening a google doc and it can't find the content), except you can navigate to a hidden link called "toggle screen reader support".

I think we'd need to work with the Docs team to solve this.

We can also add a line to the documentation about Select-to-Speak with docs?

I think there are two separate bugs here:
1. STS removes aria-hidden on load. I suspect this content script isn't getting triggered when STS loads. You'd have to enumerate all open tabs, and inject the content script programmatically. This is a STS bug. It has nothing to do with accessibility mode :).

2. For ChromeVox, we fire an event, 'chromevoxLoaded', to which Docs usually reacts to turn on screen reader mode. We have test coverage for this and I just manually verified. Specifically, in a page listening to 'chromevoxLoaded', if I turn on/off/on ChromeVox repeatedly, the listener gets called.

+grotival for commentary on this. Docs should be listening for this even after document load. It does not appear it does.

Good point David, I filed  crbug.com/890083  for #1.

#2 should be fine I think? repro steps:
-1- open google docs
-2- make sure a11y menu is not visible
-3- Ctlr+Alt+Z to turn a11y on in ChromeOS
-4- observe that a11y menu is now visible

I just tried and it's fine.

oh got it. It works only once.
Case that doesn't work:
-1- open google docs
-2- make sure a11y menu is not visible
-3- Ctlr+Alt+Z to turn a11y on in ChromeOS
-4- observe that a11y menu is now visible
-5- toggle docs a11y menu off
-6- Ctlr+Alt+Z to turn a11y off in ChromeOS
-7- Ctlr+Alt+Z to turn a11y on in ChromeOS
-8- observe that a11y menu is NOT visible

that's because chromeOS screen reader detector (listening for event in [1]) is unlistened ([2])

I believe stopping the unlistening at [2] should solve that case. Would it be possible to sync that w a buganizer bug and assign it to Kirti please?

If there is another case that is buggy feel free to add more details here. Thanks!

[1]: https://cs.corp.google.com/piper///depot/google3/javascript/apps/docs/a11y/chromevoxscreenreaderdetector.js?rcl=215089812&g=0&l=43
[2]: https://cs.corp.google.com/piper///depot/google3/java/com/google/apps/kix/client/app/kixapplication.js?type=cs&q=getCreateDefaultScreenReaderDetectorsFn&g=0&l=2730

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4081db2d0e361ee5e7a2bc7d22344ad068d1a6c7

commit 4081db2d0e361ee5e7a2bc7d22344ad068d1a6c7
Author: Katie D <katie@chromium.org>
Date: Mon Oct 01 22:02:29 2018

Run google docs content script on Select-to-Speak load.

This allows Google Docs opened before Select-to-Speak was
enabled to still be read.

Bug:  882968 
Change-Id: I723fcab46766983a8fe26477d2e9611e5bde1e9f
Reviewed-on: https://chromium-review.googlesource.com/1250601
Commit-Queue: Katie Dektar <katie@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595553}
[modify] https://crrev.com/4081db2d0e361ee5e7a2bc7d22344ad068d1a6c7/chrome/browser/resources/chromeos/select_to_speak/select_to_speak.js