Take the Extension Storage API out of experimental.

chrome/renderer/resources/extensions/experimental.storage_custom_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.
-
-// Custom bindings for the experimental.storage API.
-
-(function() {
-
-native function GetChromeHidden();
-
-var chromeHidden = GetChromeHidden();
-
-chromeHidden.registerCustomType('StorageNamespace',
-    function(typesAPI) {
-  var sendRequest = typesAPI.sendRequest;
-
-  function extendSchema(schema) {
-    var extendedSchema = schema.slice();
-    extendedSchema.unshift({'type': 'string'});
-    return extendedSchema;
-  }
-
-  function StorageNamespace(namespace, schema) {
-    // Binds an API function for a namespace to its browser-side call, e.g.
-    // experimental.storage.sync.get('foo') -> (binds to) ->
-    // experimental.storage.get('sync', 'foo').
-    //
-    // TODO(kalman): Put as a method on CustomBindingsObject and re-use (or
-    // even generate) for other APIs that need to do this. Same for other
-    // callers of registerCustomType().
-    function bindApiFunction(functionName) {
-      this[functionName] = function() {
-        var schema = this.parameters[functionName];
-        chromeHidden.validate(arguments, schema);
-        return sendRequest(
-            'experimental.storage.' + functionName,
-            [namespace].concat(Array.prototype.slice.call(arguments)),
-            extendSchema(schema));
-      };
-    }
-    ['get', 'set', 'remove', 'clear'].forEach(bindApiFunction.bind(this));
-  }
-
-  return StorageNamespace;
-});
-
-})();