I'm triaging a11y bugs. 

I can reproduce the issue.

I'm working on fixing this.

For context that's the button that I'm fixing.

Deleted: Screenshot from 2018-03-16 11-21-46.png 7.7 KB

	Screenshot from 2018-03-16 11-21-46.png 7.7 KB View Download

To be able to achieve this I have to change the normal behaviour of this button.

Currently this is roughly laid out as:
<button> Open <div id="trigger"> ▼ </div> </button>

The button element is what ChromeVox sees and reads as "Open button Press Search plus Space to activate".

If we press "Search + Space", ChromeVox issues a "click", like a mouse clicking or a keyboard ENTER key event.

As a mouse user if you click on the button it opens the file with the default app.

We can't really change what ChromeVox says, as in we can't change the part "Press Search plus Space to activate". So I'm proposing that we change the behaviour of this button to be always "open the dropdown list" for everybody: using Enter, mouse click or "Search + Space".

I think it makes sense, since this element is displayed as a combobox-like element and it makes easier to users that actually want to open this option, because it doesn't have to click on the small arrow "▼".

The original behaviour "just open with default app", is still available as:
1. If there is only 1 app for the selected file type (the button displays without "▼") and works as just "open".
2. User can still double click or enter on the file name.
3. User can "Enter" x2 or "Search+Space" x2 on this button to trigger the default app.

Weifang and Maria, what do you think of this change of behaviour on this button?

This sounds good to me.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ac1e8d23e94d9d0ec898433fb455a2bc52366c78

commit ac1e8d23e94d9d0ec898433fb455a2bc52366c78
Author: Luciano Pacheco <lucmult@chromium.org>
Date: Thu Mar 29 03:17:25 2018

Change open button to open the list when displayed as a combobox

Change the open button when it's displayed as a combobox to open the
options list instead of opening the file when there are more options.

Open button is only displayed as a combobox when there are more than
one application for the selected file, otherwise it's displayed as
a regular button.

This change of behavior is to make the open button (as combobox)
accessible via keyboard and screen reader (Chromevox).

IMPORTANT: This is a change of behavior, but this seems more consistent
since the UI displays the button as a combo, it's expected that enter
key or click open the combo list, instead of triggering the "open"
button which is open with default app. Users already have option to
use enter key to open the file without the "open menu".

Test: browser_test
Bug:  793723 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I8dab527805cb687103882e1b650b857fd5fb876c
Reviewed-on: https://chromium-review.googlesource.com/970048
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Sasha Morrissey <sashab@chromium.org>
Commit-Queue: Luciano Pacheco (SYD) <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546722}
[modify] https://crrev.com/ac1e8d23e94d9d0ec898433fb455a2bc52366c78/ui/file_manager/file_manager/foreground/js/ui/combobutton.js
[modify] https://crrev.com/ac1e8d23e94d9d0ec898433fb455a2bc52366c78/ui/file_manager/integration_tests/file_manager/tasks.js

The CL above fix this issue.