ppapi: Cleanup class/struct forward declarations

ppapi/tests/test_message_loop.h

 // 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.
 
 #ifndef PAPPI_TESTS_TEST_MESSAGE_LOOP_H_
 #define PAPPI_TESTS_TEST_MESSAGE_LOOP_H_
 
 #include <string>
 
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/tests/test_case.h"
 #include "ppapi/utility/completion_callback_factory.h"
 
-namespace pp {
-class MessageLoop;
-}
-
 class TestMessageLoop : public TestCase {
  public:
   explicit TestMessageLoop(TestingInstance* instance);
   virtual ~TestMessageLoop();
 
  private:
   // TestCase implementation.
   virtual void RunTests(const std::string& filter);
 
   std::string TestBasics();
@@ skipping 10 matching lines @@
   void EchoParamToMainTask(int32_t result, TestParam param);
 
   // The last test param we received in SetParamAndQuitTask (or kInvalid if
   // none).
   TestParam param_;
   pp::CompletionCallbackFactory<TestMessageLoop> callback_factory_;
   NestedEvent main_loop_task_ran_;
 };
 
 #endif  // PAPPI_TESTS_TEST_MESSAGE_LOOP_H_