Bug 1553748 - [marionette] Firefox should not unload tabs when available memory is running low. r=webdriver-reviewers,automatedtester

Differential Revision: https://phabricator.services.mozilla.com/D34145

--HG--
extra : moz-landing-system : lando

testing/marionette/client/marionette_driver/geckoinstance.py

@@ -563,6 +563,9 @@ class DesktopInstance(GeckoInstance):
         # Disable browser animations
         "toolkit.cosmeticAnimations.enabled": False,
 
+        # Don't unload tabs when available memory is running low
+        "browser.tabs.unloadOnLowMemory": False,
+
         # Do not warn when closing all open tabs
         "browser.tabs.warnOnClose": False,
         # Do not warn when closing all other open tabs

testing/marionette/components/marionette.js

@@ -131,6 +131,9 @@ const RECOMMENDED_PREFS = new Map([
   // unloaded
   ["browser.tabs.disableBackgroundZombification", false],
 
+  // Don't unload tabs when available memory is running low
+  ["browser.tabs.unloadOnLowMemory", false],
+
   // Do not warn when closing all open tabs
   ["browser.tabs.warnOnClose", false],