TestingPlatformSupport: register Platform instance correctly

third_party/WebKit/public/platform/Platform.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 121 matching lines @@
 #else
   typedef int FileHandle;
 #endif
 
   // Initialize platform and wtf. If you need to initialize the entire Blink,
   // you should use blink::initialize.
   static void initialize(Platform*);
   static void shutdown();
   static Platform* current();
 
-  // Used to switch the current platform only for testing.
+  // Used to switch the current platform only for testing. Since this method
+  // calls virtual methods internally, you should not call with self instance
+  // inside a Platform subclass's constructor.

[haraken, 2017/01/12 11:21:01]

// you should not pass in a Platform object that is not fully instantiated

[Takashi Toyoshima, 2017/01/12 12:13:02]

Done.

   static void setCurrentPlatformForTesting(Platform*);
 
   // May return null.
   virtual WebCookieJar* cookieJar() { return nullptr; }
 
   // Must return non-null.
   virtual WebClipboard* clipboard() { return nullptr; }
 
   // Must return non-null.
   virtual WebFileUtilities* fileUtilities() { return nullptr; }
@@ skipping 524 matching lines @@
  protected:
   Platform();
   virtual ~Platform() {}
 
   WebThread* m_mainThread;
 };
 
 }  // namespace blink
 
 #endif