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

tools/json_schema_compiler/model.py

Index: tools/json_schema_compiler/model.py
diff --git a/tools/json_schema_compiler/model.py b/tools/json_schema_compiler/model.py
index e0147b5b4889fb2a86b59a74648a4deb24316051..6dc87a964ecf9644b3e6c588dc40732d2130ce67 100644
--- a/tools/json_schema_compiler/model.py
+++ b/tools/json_schema_compiler/model.py
@@ -183,6 +183,7 @@ class Type(object):
     self.simple_name = _StripNamespace(self.name, namespace)
     self.unix_name = UnixName(self.name)
     self.description = json.get('description', None)
+    self.jsexterns = json.get('jsexterns', None)
     self.origin = origin
     self.parent = parent
     self.instance_of = json.get('isInstanceOf', None)
@@ -317,8 +318,9 @@ class Function(object):
     self.filters = [GeneratePropertyFromParam(filter_instance)
                     for filter_instance in json.get('filters', [])]
     callback_param = None
-    for param in json.get('parameters', []):
-      if param.get('type') == 'function':
+    params = json.get('parameters', [])
+    for i, param in enumerate(params):
+      if param.get('type') == 'function' and i == len(params) - 1:
         if callback_param:
           # No ParseException because the webstore has this.
           # Instead, pretend all intermediate callbacks are properties.