i guess this would resolve  issue 720082  ?

It would certainly do that for our relays, yes.

I think it'd be more elegant to have the relay tell the client that it does not support reconnects.

This could be done in the response from /cookie or in the response from /proxy. I would prefer the latter because then this can be toggled per session. On the other hand, putting this in /proxy depends on making /proxy more friendly to extension, for which there is a proposal at https://goto.google.com/straightforward-slash-proxy (if I recall the link correctly).

 Issue 720082  has been merged into this issue.

 Issue 895545  has been merged into this issue.

I don't think  Issue 895545  is really a dup of this, since I was asking for something different - a way to get out of the Retrying... state and actually reconnect (which does work).

If retry doesn't work (within a reasonable timeout - maybe 5-30 seconds?), it should revert to the same prompt I get when I disconnect manually, to "(R)econnect, (C)hoose another connection, or E(x)it?"

And while in the Retrying... state, there should be a key sequence (which should be shown in the overlay, e.g. "Retrying... (press Shift-Ctrl-WTF to abort)") to escape immediately to the above prompt, or back to the choose-a-connection page.

The following revision refers to this bug:
  https://chromium.googlesource.com/apps/libapps/+/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767

commit 5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767
Author: Mike Frysinger <vapier@chromium.org>
Date: Tue Jan 08 21:40:24 2019

nassh: make relay connection resume an option

The Google relay has never supported connection resumption, so stop
trying to use it.

Bug:  chromium:728275 
Change-Id: Ibd6ec8726e1c4eb2d33956b149aea318f1c06ee0
Reviewed-on: https://chromium-review.googlesource.com/c/1399825
Reviewed-by: Vitaliy Shipitsyn <vsh@google.com>
Tested-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767/nassh/js/nassh_command_instance.js
[modify] https://crrev.com/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767/nassh/html/nassh_connect_dialog.html
[modify] https://crrev.com/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767/nassh/js/nassh_stream_google_relay.js
[modify] https://crrev.com/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767/nassh/doc/options.md
[modify] https://crrev.com/5012c6ed4cbe57bd9dbbf91489b8134cb5a6c767/nassh/js/nassh_google_relay.js

> since I was asking for something different - a way to get out of the Retrying... state and actually reconnect

you can do that already.  press:
  Enter ~ .
that will break the connection at any time.  this is standard OpenSSH commands, not something specific to Secure Shell.

i've changed the default Google relay usage so that we don't try to resume at all now