GeckoView does not store a list of all GeckoSessions by design.

Embedders might keep some GeckoSessions internally and only feed them to GeckoView whenever they need to display the page to the user.

Extension can "unload" tabs using the https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/tabs/discard API, and can get a list of all tabs (including the discarded ones).

We need to add a delegate in GeckoView to let embedders provide the full list of GeckoSessions when needed by extensions and one to "unload" a tab using the tabs.discard API.

Blocking browser.tabs meta bug 1543755

Mass moving bugs to the Extension component.

A way to implement this could be the following:

• Add TabDetails to WebExtension: https://searchfox.org/mozilla-central/rev/c59d9181cbcd8356ce9271723e31be11641e7010/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/WebExtension.java#29, TabDetails can just be a data class that contains either a GeckoSession (if the tab is loaded) or all details for a "discarded" tab, roughly mimicking the tabs.Tag object: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/Tabs/Tab, something like this:

public class TabDetails {
     // Either this
     public GeckoSession session;
     // or all of these
     public String sessionContextId;
     public String favIconUrl;
     public int id;
     public boolean isPrivateBrowsing;
     public String title;
     public String url;
}

• Add GeckoResult<List<TabDetails>> onTabList() here: https://searchfox.org/mozilla-central/rev/c59d9181cbcd8356ce9271723e31be11641e7010/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/WebExtension.java#762
  this method will be called whenever the extension calls tabs.query or any other method that needs the list of tabs.
• Rewrite windowTracker.getAll to call onTabList() instead and use that if the embedder returns a non-null value: https://searchfox.org/mozilla-central/rev/c59d9181cbcd8356ce9271723e31be11641e7010/mobile/android/components/extensions/ext-android.js#577-585 (the reason why window even though these are tabs is... interesting... I can get into that if needed), if we have a list the getAll method would return one window with a list of tabs in it (probably will have to have a custom Window class that extends from this https://searchfox.org/mozilla-central/source/mobile/android/components/extensions/ext-android.js#518), an example on how to query the embedder can be found here: https://hg.mozilla.org/mozilla-central/rev/fa01d9615f6d3fd93488178f2e5945ab600521c1 (in this patch the extension is calling openOptionsPage which causes GeckoView to call onOpenOptionsPage)

The bug assignee is inactive on Bugzilla, so the assignee is being reset.

Tasks and enhancements should have severity N/A.

When this is being worked on, please verify the scenarios described in Bug 1465828.

Note that with the coming opening up of the add on store this is going to prevent some add ons coming to Fenix