Add support for using AMD modules from extensions modules.

chrome/renderer/extensions/module_system_unittest.cc

 // 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.
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/test/base/module_system_test.h"
 #include "extensions/renderer/module_system.h"
 
 // TODO(cduvall/kalman): Put this file in extensions namespace.
 using extensions::ModuleSystem;
@@ skipping 255 matching lines @@
 
 TEST_F(ModuleSystemTest, TestOverrideNonExistentNativeHandler) {
   ModuleSystem::NativesEnabledScope natives_enabled_scope(
       context_->module_system());
   OverrideNativeHandler("thing", "exports.x = 5;");
   RegisterModule("test",
       "var assert = requireNative('assert');"
       "assert.AssertTrue(requireNative('thing').x == 5);");
   context_->module_system()->Require("test");
 }
+
+TEST_F(ModuleSystemTest, TestRequireAsync) {
+  ModuleSystem::NativesEnabledScope natives_enabled_scope(
+      context_->module_system());
+  RegisterModule("add",
+                 "define('add', [], function() {"
+                 "  return { Add: function(x, y) { return x + y; } };"
+                 "});");
+  RegisterModule("math",
+                 "define('math', ['add'], function(add) {"
+                 "  return { Add: add.Add };"
+                 "});");
+  RegisterModule("test",
+                 "requireAsync('math').then(function(math) {"

[not at google - send to devlin, 2014/07/02 22:07:45]

could you also test
- a chain of requireAsync calls
- multiple outgoing requireAsync calls for the same context
- some kind of interaction with require-not-async.

Ideally I'd like to test these across contexts, but for that you'll need some
extra test setup to actually create cross-context module systems (i.e. rather
than have everything created only in the constructor, you'll need a way to
create extra contexts). and delete one or both. is that feasible?

[Sam McNally, 2014/07/03 10:56:53]

Done.
I think it may be feasible, but it looks like it'd be a decent chunk of effort
to set up an extra context.

[Sam McNally, 2014/07/07 05:58:37]

Added some cross-context tests too.

+                 "  requireNative('assert').AssertTrue(math.Add(3, 5) == 8);"
+                 "});");
+  context_->module_system()->Require("test");
+
+  // The requireAsync promise is resolved asynchronously so we need to let it
+  // run.
+  isolate_holder_.isolate()->RunMicrotasks();
+}