Supporting more APIs with json_schema_compiler

tools/json_schema_compiler/test/tabs.json

 [
   {
     "namespace": "tabs",
     "compile": true,
     "types": [
       {
         "id": "Tab",
         "type": "object",
         "properties": {
           "id": {"type": "integer", "minimum": 0, "description": "The ID of the tab. Tab IDs are unique within a browser session."},
@@ skipping 320 matching lines @@
             "minimum": 0,
             "optional": true,
             "description": "Defaults to the selected tab of the <a href='windows.html#current-window'>current window</a>."
           },
           {
             "type": "object",
             "name": "updateProperties",
             "properties": {
               "url": {
                 "optional": true,
+                "type": "string",
                 "description": "A URL to navigate the tab to."
               },
               "active": {
                 "type": "boolean",
                 "optional": true,
                 "description": "Whether the tab should be active."
               },
               "highlighted": {
                 "type": "boolean",
                 "optional": true,
@@ skipping 409 matching lines @@
             "name": "removeInfo",
             "properties": {
               "isWindowClosing": {"type": "boolean", "description": "True when the tab is being closed because its window is being closed." }
             }
           }
         ]
       }
     ]
   }
 ]