Bug 1737860 - Make the minimum inactive duration configurable through…

… pref. r=haik

For end-to-end testing, this value needs to be configurable.

Differential Revision: https://phabricator.services.mozilla.com/D129731

browser/app/profile/firefox.js

@@ -676,6 +676,10 @@ pref("security.allow_parent_unrestricted_js_loads", false);
 // Unload tabs when available memory is running low
 pref("browser.tabs.unloadOnLowMemory", true);
 
+// Tab Unloader does not unload tabs whose last inactive period is longer than
+// this value (in milliseconds).
+pref("browser.tabs.min_inactive_duration_before_unload", 600000);
+
 #if defined(XP_MACOSX)
   // During low memory periods, poll with this frequency (milliseconds)
   // until memory is no longer low. Changes to the pref take effect immediately.

browser/modules/TabUnloader.jsm

@@ -31,7 +31,9 @@ const NEVER_DISCARD = 100000;
 
 // Default minimum inactive duration.  Tabs that were accessed in the last
 // period of this duration are not unloaded.
-const kMinInactiveDurationInMs = 600000; // ten minutes
+const kMinInactiveDurationInMs = Services.prefs.getIntPref(
+  "browser.tabs.min_inactive_duration_before_unload"
+);
 
 let criteriaTypes = [
   ["isNonDiscardable", NEVER_DISCARD],