Update from https://crrev.com/327068

mojo/tools/mopy/gn_unittest.py

Index: mojo/tools/mopy/gn_unittest.py
diff --git a/mojo/tools/mopy/gn_unittest.py b/mojo/tools/mopy/gn_unittest.py
index 1aaaa6c94fd45fc99d73b61f5c5fc7065afed37a..0e8768a71223199970851a29b4716ee5f6b0dff8 100644
--- a/mojo/tools/mopy/gn_unittest.py
+++ b/mojo/tools/mopy/gn_unittest.py
@@ -37,7 +37,7 @@ class GTestListTestsTest(unittest.TestCase):
   def testGNToConfigToGN(self):
     """Tests that gn to config to gn is the identity"""
     configs_to_test = {
-      "os": [None, "android", "chromeos"],
+      "target_os": [None, "android", "chromeos"],
       "target_cpu": ["x86", "x64", "arm"],
       "is_debug": [False, True],
       "is_clang": [False, True],
@@ -49,10 +49,10 @@ class GTestListTestsTest(unittest.TestCase):
     }
 
     for args in _iterate_over_config(configs_to_test):
-      if args.get('os', None) == "chromeos":
-        args['use_glib'] = False
-        args['use_system_harfbuzz'] = False
-      if args.get('os', None) is None and sys.platform[:5] == 'linux':
+      if args.get("target_os", None) == "chromeos":
+        args["use_glib"] = False
+        args["use_system_harfbuzz"] = False
+      if args.get("target_os", None) is None and sys.platform[:5] == "linux":
         args["use_aura"] = False
         args["use_glib"] = False
         args["use_system_harfbuzz"] = False