Extension Storage API: expose storage quota information to extensions, via:

chrome/renderer/resources/extensions/schema_generated_bindings.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This script contains privileged chrome extension related javascript APIs.
 // It is loaded by pages whose URL has the chrome-extension protocol.
 
 var chrome = chrome || {};
 (function() {
   native function GetChromeHidden();
@@ skipping 475 matching lines @@
                 var constructor = customTypes[property["$ref"]];
                 if (!constructor)
                   throw new Error("No custom binding for " + property["$ref"]);
                 var args = value;
                 // For an object property, |value| is an array of constructor
                 // arguments, but we want to pass the arguments directly
                 // (i.e. not as an array), so we have to fake calling |new| on
                 // the constructor.
                 value = { __proto__: constructor.prototype };
                 constructor.apply(value, args);
+                // Recursively add properties.
+                addProperties(value, property);
               } else if (property.type === 'object') {
                 // Recursively add properties.
                 addProperties(value, property);
               } else if (property.type !== 'string') {
                 throw "NOT IMPLEMENTED (extension_api.json error): Cannot " +
                     "parse values for type \"" + property.type + "\"";
               }
             }
             if (value) {
               m[prop] = value;
@@ skipping 40 matching lines @@
     // See http://crbug.com/100242
     if (apiExists("webstorePrivate")) {
       chrome.webstorePrivate.beginInstallWithManifest2 =
           chrome.webstorePrivate.beginInstallWithManifest3;
     }
 
     if (apiExists("test"))
       chrome.test.getApiDefinitions = GetExtensionAPIDefinition;
   });
 })();