Implement a module system for the extension bindings JS.

chrome/renderer/resources/extensions/setup_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.
+
+var contextInfo = requireNative('context_info');
+var sgb = requireNative('schema_generated_bindings');
+
+require('miscellaneous_bindings');
+require('schema_generated_bindings');
+require('apitest');
+
+// Load the custom bindings for each API.
+sgb.GetExtensionAPIDefinition().forEach(function(apiDef) {
+  if (contextInfo.IsAPIAllowed(apiDef.namespace))
+    require(apiDef.namespace);
+});