Use ScopedTaskEnvironment instead of MessageLoop in tests that use v8.

content/test/ppapi_unittest.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_TEST_PPAPI_UNITTEST_H_
 #define CONTENT_TEST_PPAPI_UNITTEST_H_
 
-#include <memory>
-
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/test/scoped_task_environment.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace base {
-class MessageLoop;
-}
-
 namespace content {
 
 class PepperPluginInstanceImpl;
 class PluginModule;
 
 class PpapiUnittest : public testing::Test {
  public:
   PpapiUnittest();
   ~PpapiUnittest() override;
 
   void SetUp() override;
   void TearDown() override;
 
   PluginModule* module() const { return module_.get(); }
   PepperPluginInstanceImpl* instance() const { return instance_.get(); }
 
   // Provides access to the interfaces implemented by the test. The default one
   // implements PPP_INSTANCE.
   virtual const void* GetMockInterface(const char* interface_name) const;
 
   // Deletes the instance and module to simulate module shutdown.
   void ShutdownModule();
 
   // Sets the view size of the plugin instance.
   void SetViewSize(int width, int height) const;
 
  private:
-  // Note: module must be declared first since we want it to get destroyed last.
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
+
+  // Note: module must be declared right after |scoped_task_environment_| since
+  // we want it to get destroyed just before |scoped_task_environment_|.
   scoped_refptr<PluginModule> module_;
   scoped_refptr<PepperPluginInstanceImpl> instance_;
 
-  std::unique_ptr<base::MessageLoop> message_loop_;
-
   DISALLOW_COPY_AND_ASSIGN(PpapiUnittest);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_TEST_PPAPI_UNITTEST_H_