After this CL(http://crrev.com/c/1202146), the actual result will be VoiceOver reading out the content on IncognitoTabGrid instead of RemoteTabGrid, and the TabGridEmptyStateView of IncognitoTabGrid will also be located at the left border of the screen.

At commit 74bcb873aea383378c399c7c4fe753605f0fa45e, I actually don't see this issue anymore, because when you close all regular tabs, open VoiceOver, and return back to the app, a new tab is automatically opened. Thus, this issue is not an edge case anymore.

There is still some funky business with regards to switching pages and asking VoiceOver to read out all contents. If you select something on Incognito Tabs, swipe over to Regular Tabs, and then 2-finger swipe down, it will read the contents of Incognito instead of Regular Tabs.

I think this issue still exists, you can test it on iPad. Open chrome with only one regular tab, open VoiceOver, close that tab by tapping the "X" on the tab and get into Regular TabGrid, then do a double finger down swipe to read through the page. I test it on 005a710c3b3c515ec0fa91bd70482bd4339ce586 and the bug is now even weirder: it first reads the Incognito TabGrid, and then skip the Regular TabGrid and reads the Remote TabGrid. ╮(╯▽╰)╭

Can you provide a video? I'm a bit confused. From what I see, it's not possible to tap the "X" on a tab to close it.

https://drive.google.com/open?id=1CjzIf0QAmT-n_D21xSFd0vyPYHf2PiK8

You can just single-tap to choose the "X" of the tab and then double-tap to close it.

Ok yeah I can repro. marq@ what is the intended behavior here? Do we just want to read out the current page or do we want VoiceOver to go across all three pages the read them? I feel like it should be the former, but maybe that doesn't inform the user that there are other pages. 

One thing I noticed was that we are not updating _currentPage for accessibility scrolls, because an accessibility scroll is neither scrollView.dragging nor scrollView.decelerating, so the entire logic in scrollViewDidScroll: is skipped. This also explains why the pagecontrol isn't updated (not that important for accessibility, but it just shows that the whole page management collapses in Voiceover).

I also am noticing that on iphone devices, voiceover doesn't seem to allow a user to select anything on a page that the user 3-finger swipes over to. There overall seems to be many unresolved issues with tabgrid accessibility.

One way to potentially fix most of these problems is to toggle which page can be focused on by VoiceOver by setting accessibilityElementsHidden. However, we need to always have the accurate _currentPage for that to be achieved.

I'm going to assume that when a user asks VoiceOver to readout, it should only read out the contents of the page that is visible. The user can be known of other pages by tapping on the pagecontrol.

I made a very simple paged UIScrollView with 3 pages, and I found out that voiceover will read out something like "page 1 of 3" when user do 3-finger-swipe to change page. I think it would be better if we can keep that in our ScrollView or make something similar, instead of read out everything on all pages.

We replace the "page 1 of 3" with whatever we return in accessibilityScrollStatusForScrollView:, but that is only when the user swipes to different pages. That was actually broken in the current implementation because we weren't properly updating _currentPage when a user 3-finger swiped. I'm pushing out a CL that fixes that.

My fix also will cause read outs to vocalize only the contents of the visible page when the use 2-finger swipes down.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fbe67a9526a8ada8ab37b2ce9e7b66dd5a39cdae

commit fbe67a9526a8ada8ab37b2ce9e7b66dd5a39cdae
Author: Chris Lu <thegreenfrog@chromium.org>
Date: Thu Sep 20 15:55:05 2018

[ios] Fix VoiceOver Issues in Tabgrid

- Updates _currentPage properly in response to 3-finger accessibility swipe. This will now properly read out the currently visible page if a user swipes to a different page.
- Ensures that only the currently visible page's elements can be selected in the scroll view. This resolves an issue VoiceOver was having with what page to readout and to focus on. Oftentimes the visible page was not readout or selectable.

Video: https://drive.google.com/open?id=1Q62MUlrVcNlqnFIQOfw_YiGHinTKb_45

Bug:  880079 
Change-Id: I0696786292bec375af9d5326a790700000114559
Reviewed-on: https://chromium-review.googlesource.com/1221474
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592818}
[modify] https://crrev.com/fbe67a9526a8ada8ab37b2ce9e7b66dd5a39cdae/ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.mm

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/093ee96f6f1a76f10cfb65b1302b746343f0419b

commit 093ee96f6f1a76f10cfb65b1302b746343f0419b
Author: Justin Cohen <justincohen@chromium.org>
Date: Thu Sep 20 20:47:21 2018

Revert "[ios] Fix VoiceOver Issues in Tabgrid"

This reverts commit fbe67a9526a8ada8ab37b2ce9e7b66dd5a39cdae.

Reason for revert: Breaks TabSwitcherTransitionTestCase\testRotationsWhileSwitcherIsNotActive

Original change's description:
> [ios] Fix VoiceOver Issues in Tabgrid
> 
> - Updates _currentPage properly in response to 3-finger accessibility swipe. This will now properly read out the currently visible page if a user swipes to a different page.
> - Ensures that only the currently visible page's elements can be selected in the scroll view. This resolves an issue VoiceOver was having with what page to readout and to focus on. Oftentimes the visible page was not readout or selectable.
> 
> Video: https://drive.google.com/open?id=1Q62MUlrVcNlqnFIQOfw_YiGHinTKb_45
> 
> Bug:  880079 
> Change-Id: I0696786292bec375af9d5326a790700000114559
> Reviewed-on: https://chromium-review.googlesource.com/1221474
> Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
> Reviewed-by: Mark Cogan <marq@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#592818}

TBR=marq@chromium.org,thegreenfrog@chromium.org

Change-Id: Idb378ca1c1a1405275975e47956ac94d09865ab1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  880079 
Reviewed-on: https://chromium-review.googlesource.com/1237174
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592937}
[modify] https://crrev.com/093ee96f6f1a76f10cfb65b1302b746343f0419b/ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.mm

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d94921c05ff2c745fbb0c3881fd5811eb13a4ff2

commit d94921c05ff2c745fbb0c3881fd5811eb13a4ff2
Author: Chris Lu <thegreenfrog@chromium.org>
Date: Fri Sep 28 13:52:55 2018

[ios] Fix VoiceOver Issues in Tabgrid

- Updates _currentPage properly in response to 3-finger accessibility swipe. This will now properly read out the currently visible page if a user swipes to a different page.
- Ensures that only the currently visible page's elements can be selected in the scroll view. This resolves an issue VoiceOver was having with what page to readout and to focus on. Oftentimes the visible page was not readout or selectable.

Video: https://drive.google.com/open?id=1Q62MUlrVcNlqnFIQOfw_YiGHinTKb_45

Bug:  880079 
Change-Id: Ic9a91762e9a5f04b267ac588c83a675d61bd53cf
Reviewed-on: https://chromium-review.googlesource.com/1221474
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#592818}
Reviewed-on: https://chromium-review.googlesource.com/1238995
Cr-Commit-Position: refs/heads/master@{#595075}
[modify] https://crrev.com/d94921c05ff2c745fbb0c3881fd5811eb13a4ff2/ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.mm

Verified on Canary on 10/2