Bug 1535026 - [marionette] 'mach marionette-test' should force e10s disabled for Fennec. r=ato

Differential Revision: https://phabricator.services.mozilla.com/D23401

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

testing/marionette/doc/Testing.md

@@ -102,7 +102,7 @@ for additional options.
 Alternately, you can start an emulator yourself and have the Marionette runner
 start Fennec for you:
 
-    % ./mach marionette-test --emulator --app='fennec' --address=127.0.0.1:2828 --disable-e10s
+    % ./mach marionette-test --emulator --app='fennec' --address=127.0.0.1:2828
 
 To connect to an already-running Fennec in an already running emulator or on a device, you will need to enable Marionette manually by setting the browser preference
 `marionette.enabled` set to true in the Fennec profile.
@@ -113,7 +113,7 @@ Make sure port 2828 is forwarded:
 
 If Fennec is already started:
 
-    % ./mach marionette-test --app='fennec' --address=127.0.0.1:2828 --disable-e10s
+    % ./mach marionette-test --app='fennec' --address=127.0.0.1:2828
 
 If Fennec is not already started on the emulator/device, add the `--emulator`
 option. Marionette Test Runner will take care of forwarding the port and

testing/marionette/mach_commands.py

@@ -78,6 +78,11 @@ class MarionetteTest(MachCommandBase):
                 tests.append(obj["file_relpath"])
             del kwargs["test_objects"]
 
+        # Force disable e10s because it is not supported in Fennec
+        if "fennec" in kwargs.get("app"):
+            kwargs["e10s"] = False
+
         if not kwargs.get("binary") and conditions.is_firefox(self):
             kwargs["binary"] = self.get_binary_path("app")
+
         return run_marionette(tests, topsrcdir=self.topsrcdir, **kwargs)