1256602 - Better async API for `outerWindowID`

Status: RESOLVED INCOMPLETE

(Core :: DOM: Content Processes, defect)

Description

[sergz]

User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36

Steps to reproduce:

To reproduce the bug one can try the following code in the Browser console:

let browser = window.getBrowser();
let tab = browser.addTab("about:blank");
console.log(tab.linkedBrowser.outerWindowID);
setTimeout(function(){console.log(tab.linkedBrowser.outerWindowID);}, 20);

JIC, in my extension the code is executed in chrome process and `window` is `Services.wm.getMostRecentWindow("navigator:browser");`.


Actual results:

Actual results:
In e10s `tab.linkedBrowser.outerWindowID` is firstly `null` however after some delay (~20msec on my machine) it is initialized to the actual number (e.g. 2147483652).
In FF 45 `tab.linkedBrowser.outerWindowID` is always already initialized to some number.



Expected results:

Expected results:
`tab.linkedBrowser.outerWindowID` should be already initialized to the actual number after the returning from `browser.addTab("about:blank")`.


Generally speaking it may be not an issue that it is initialized in a background however what is the reliable way to be notified when it's ready in that case?

Comment 1

[Mike Conley (:mconley) (:⚙️)]

Hey sergz,

When the remote browser is loaded, it sends a sync "Browser:Init" message up to the parent to inform the parent of the outerWindowId.

In the future, we might want to add some code to browser.xml / remote-browser.xml that returns a Promise that resolves when the outerWindowId is available, but for now, you can maybe work around this by listening for the Browser:Init message on the browser that has opened.

Comment 2

[Andrew Overholt [:overholt]]

Mike, I'm marking this as "backlog" but if you think it'll be fixed in the new few months, feel free to mark it as "fixlater" or even "fixnow".

Comment 3

[sergz]

(In reply to Mike Conley (:mconley) - (needinfo me!) from comment #1)
> When the remote browser is loaded, it sends a sync "Browser:Init" message up
> to the parent to inform the parent of the outerWindowId.
That works good, thanks a lot.

Comment 4

[Firefox Bug Husbandry Bot]

With Firefox 57 only WebExtensions are permitted and are, by default, e10s compatible.