Reland of Adding task runner/ message loop to tests that use IsolateHolder.

gin/modules/module_registry_unittest.cc

 // Copyright 2014 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 "gin/modules/module_registry.h"
 
 #include "base/bind.h"
-#include "base/message_loop/message_loop.h"
 #include "gin/modules/module_registry_observer.h"
 #include "gin/modules/module_runner_delegate.h"
 #include "gin/public/context_holder.h"
 #include "gin/public/isolate_holder.h"
 #include "gin/shell_runner.h"
 #include "gin/test/v8_test.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 
 namespace {
 
 struct TestHelper {
   TestHelper(v8::Isolate* isolate)
       : delegate(std::vector<base::FilePath>()),
         runner(new ShellRunner(&delegate, isolate)),
         scope(runner.get()) {
   }
 
-  base::MessageLoop message_loop;
   ModuleRunnerDelegate delegate;
   scoped_ptr<ShellRunner> runner;
   Runner::Scope scope;
 };
 
 class ModuleRegistryObserverImpl : public ModuleRegistryObserver {
  public:
   ModuleRegistryObserverImpl() : did_add_count_(0) {}
 
   void OnDidAddPendingModule(
@@ skipping 116 matching lines @@
   helper.runner->Run(source, "script");
   EXPECT_EQ(no_such_module_set, registry->unsatisfied_dependencies());
 
   // Should have no effect on the unsatisfied_dependencies set.
   ModuleRegistry::LoadModuleCallback callback = base::Bind(OnModuleLoadedNoOp);
   registry->LoadModule(instance_->isolate(), "one", callback);
   EXPECT_EQ(no_such_module_set, registry->unsatisfied_dependencies());
 }
 
 }  // namespace gin