Re-land: Update json_schema_compiler to handle the Automation extension API

tools/json_schema_compiler/idl_schema_test.py

Index: tools/json_schema_compiler/idl_schema_test.py
diff --git a/tools/json_schema_compiler/idl_schema_test.py b/tools/json_schema_compiler/idl_schema_test.py
index 3e0d3cc482a0cda344a4d3f66bd23cccfa0dcaef..f9a4d8702a7ab12a6113c1db6b880d5650a70e7c 100755
--- a/tools/json_schema_compiler/idl_schema_test.py
+++ b/tools/json_schema_compiler/idl_schema_test.py
@@ -70,7 +70,8 @@ class IdlSchemaTest(unittest.TestCase):
   def testLegalValues(self):
     self.assertEquals({
         'x': {'name': 'x', 'type': 'integer', 'enum': [1,2],
-              'description': 'This comment tests "double-quotes".'},
+              'description': 'This comment tests "double-quotes".',
+              'jsexterns': None},
         'y': {'name': 'y', 'type': 'string'},
         'z': {'name': 'z', 'type': 'string'},
         'a': {'name': 'a', 'type': 'string'},
@@ -402,21 +403,25 @@ class IdlSchemaTest(unittest.TestCase):
     self.assertEquals(OrderedDict([
       ('first', OrderedDict([
         ('description', 'Integer property.'),
+        ('jsexterns', None),
         ('type', 'integer'),
         ('value', 42),
       ])),
       ('second', OrderedDict([
         ('description', 'Double property.'),
+        ('jsexterns', None),
         ('type', 'number'),
         ('value', 42.0),
       ])),
       ('third', OrderedDict([
         ('description', 'String property.'),
+        ('jsexterns', None),
         ('type', 'string'),
         ('value', 'hello world'),
       ])),
       ('fourth', OrderedDict([
         ('description', 'Unvalued property.'),
+        ('jsexterns', None),
         ('type', 'integer'),
       ])),
     ]), schema.get('properties'))