Bug 1271911 - Enable the browser.tabs.remote.force-enable preference when using e10s. r=maja_zf

MozReview-Commit-ID: BWqRrhPx7h8

--HG--
extra : rebase_source : 052600e039ff21d7e47fd26bb8f078863625a4b6

testing/marionette/harness/marionette/runner/base.py

@@ -437,6 +437,7 @@ class BaseMarionetteArguments(ArgumentParser):
         if args.e10s:
             args.prefs.update({
                 'browser.tabs.remote.autostart': True,
+                'browser.tabs.remote.force-enable': True,
                 'extensions.e10sBlocksEnabling': False
             })
 

testing/marionette/harness/session/runner/base.py

@@ -406,6 +406,7 @@ class BaseSessionArguments(ArgumentParser):
         if args.e10s:
             args.prefs.update({
                 'browser.tabs.remote.autostart': True,
+                'browser.tabs.remote.force-enable': True,
                 'extensions.e10sBlocksEnabling': False
             })