Bug 1019043 - Return None when getting the device manager in B2GTestCaseMixin if target is B2G desktop. r=mdas

testing/marionette/client/marionette/runner/mixins/b2g.py

@@ -44,7 +44,8 @@ class B2GTestCaseMixin(object):
         self._device_manager = None
 
     def get_device_manager(self, *args, **kwargs):
-        if not self._device_manager:
+        capabilities = self.marionette.session_capabilities
+        if not self._device_manager and capabilities['device'] != 'desktop':
             self._device_manager = get_dm(self.marionette, **kwargs)
         return self._device_manager
 
@@ -52,6 +53,7 @@ class B2GTestCaseMixin(object):
     def device_manager(self):
         return self.get_device_manager()
 
+
 class B2GTestResultMixin(object):
 
     def __init__(self, *args, **kwargs):