Make it possible to enable/disable specific ppapi tests. Migrate PostMessage tests.

ppapi/tests/test_core.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 PPAPI_TEST_TEST_CORE_H_
 #define PPAPI_TEST_TEST_CORE_H_
 
 #include <string>
 
 #include "ppapi/tests/test_case.h"
 
 struct PPB_Core;
 
 class TestCore : public TestCase {
  public:
   explicit TestCore(TestingInstance* instance) : TestCase(instance) {}
 
  private:
   // TestCase implementation.
   virtual bool Init();
-  virtual void RunTest();
+  virtual void RunTests(const std::string& filter);
 
   std::string TestTime();
   std::string TestTimeTicks();
 
 };
 
 #endif  // PPAPI_TEST_TEST_CORE_H_