The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a012803534f9b350949a1ccf6bdad2d60e152b27

commit a012803534f9b350949a1ccf6bdad2d60e152b27
Author: edchin <edchin@chromium.org>
Date: Mon Mar 05 18:58:40 2018

[ios] First pass at accessibility on tab grid

Bug:  818442 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ia7a185c4c2ffdffcee4bb5072a838ddaa345ebdc
Reviewed-on: https://chromium-review.googlesource.com/947891
Commit-Queue: edchin <edchin@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540885}
[modify] https://crrev.com/a012803534f9b350949a1ccf6bdad2d60e152b27/ios/chrome/browser/ui/tab_grid/BUILD.gn
[modify] https://crrev.com/a012803534f9b350949a1ccf6bdad2d60e152b27/ios/chrome/browser/ui/tab_grid/grid_cell.h
[modify] https://crrev.com/a012803534f9b350949a1ccf6bdad2d60e152b27/ios/chrome/browser/ui/tab_grid/grid_cell.mm
[modify] https://crrev.com/a012803534f9b350949a1ccf6bdad2d60e152b27/ios/chrome/browser/ui/tab_grid/tab_grid_view_controller.mm

The CL above, though it is titled first pass, it implements all the accessibility for S-See-Open-Tabs.

The NextAction date has arrived: 2018-03-14

Re-opening this because I found accessibility behavior in the stack_view that is better than the behavior in the tab_switcher, and which I did not yet implement. 
The stack_view says something like: "Incognito tabs 4-10, of 35".

Chat that includes some tips/context:
There "page" is always singular, but we will potentially have a plural number of tabs. 

We need to handle the case where there's only one tab without sounding dumb ("tabs 1 to 1 of 1"). 

We need to make sure that the plurality of "tabs" matches the total number of tabs, so in your example, "tabs" needs to be pluralized for the number 24.

This matters because some languages don't use the same plural inflection for all numbers.
(And we shouldn't use a less-natural phrase just because getting this right is tricky.)

There are some technical barriers related to VoiceOver that I has prevented this story from completion. I am putting this work aside for now, given it is not high priority. I have filed a radar, and will work on this in Q2. 

I'm simply going to do one last test of accessibility before closing this out.