1510806 - [meta] Make RDM Fission-ready

Status: RESOLVED DUPLICATE of bug 1574885

(DevTools :: Responsive Design Mode, enhancement, P3)

Description

[Mike Conley (:mconley) (:⚙️)]

It looks like RDM currently closes the UI when the process flips for a tab. With Fission, we should expect many process flips to occur. We should probably make RDM resilient to that.

Comment 1

[Brad Werth [:bradwerth]]

Agreed we need to fix this for Fission. Is there a convenient way to force a process flip, for purposes of testing?

Comment 2

[Mike Conley (:mconley) (:⚙️)]

(In reply to Brad Werth [:bradwerth] from comment #1)
> Agreed we need to fix this for Fission. Is there a convenient way to force a
> process flip, for purposes of testing?

At this stage, yes you can[1], but you might want to connect with Nika from DOM to see how they're planning on re-architecting our process-flipping stuff for Fission. I think she's planning on putting most of that logic somewhere in the networking layer in the parent process.

Nika, do you have any published plans anywhere on how process flipping is going to work in the future that bradwerth can look at?

[1]: Here's one way of doing it with the current infrastructure on Nightly:

1. Visit https://www.mozilla.org
2. Enter RDM
3. Browse to about:newtab

ER: RDM should stay open
AR: RDM closes and about:newtab is loaded in the full page.

Comment 3

[Mike Conley (:mconley) (:⚙️)]

ni? to nika for comment 2.

Comment 4

[Nika Layzell [:nika] (ni? for response)]

Other pages which you can load to trigger a swap include:
1. Loading file:// URIs
2. Loading moz-extension:// URIs
3. Loading about:config or other chrome-only pages
4. Loading about:newtab (I think nightly only)
5. Switching from any of these URIs to any other of these URIs.

IIRC the way that RDM works is by placing a chrome document inside the xul:browser, and forwarding messages from the outer xul:browser into an <iframe mozbrowser> internally. When we do a process switch we currently trigger that switch by replacing the xul:browser element in the DOM. 

As we move to a new system for doing process swaps without replacing the browser node for fission, this may be changed. It may not be worthwhile to fix the issue for the current system of process switching given the changes coming down the pipe.