Clean up WebDOMEvent ownership of WebCore::Event.

public/platform/WebPrivatePtr.h

 /*
  * Copyright (C) 2010 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 23 matching lines @@
 #include "WebCommon.h"
 
 #if WEBKIT_IMPLEMENTATION
 #include <wtf/PassRefPtr.h>
 #endif
 
 namespace WebKit {
 
 // This class is an implementation detail of the WebKit API.  It exists
 // to help simplify the implementation of WebKit interfaces that merely
 // wrap a reference counted WebCore class.

[darin (slow to review), 2013/05/22 20:28:22]

optional:  it might be nice to provide sample code of how to properly use
WebPrivatePtr.

[dmichael (off chromium), 2013/05/22 20:54:29]

Good suggestion. Done.

 template <typename T>
 class WebPrivatePtr {
 public:
     WebPrivatePtr() : m_ptr(0) { }
     ~WebPrivatePtr() { WEBKIT_ASSERT(!m_ptr); }
 
     bool isNull() const { return !m_ptr; }
 
 #if WEBKIT_IMPLEMENTATION
     WebPrivatePtr(const PassRefPtr<T>& prp)
@@ skipping 35 matching lines @@
 
 private:
 #if WEBKIT_IMPLEMENTATION
     void assign(T* p)
     {
         // p is already ref'd for us by the caller
         if (m_ptr)
             m_ptr->deref();
         m_ptr = p;
     }
+#else
+    // Disable assign; we define it above for when WEBKIT_IMPLEMENTATION is set,

[darin (slow to review), 2013/05/22 20:28:22]

nit: confusing to call this operator "assign" since there is an assign method. 
How about calling this "assignment operator" instead?

[dmichael (off chromium), 2013/05/22 20:54:29]

Good point, done.

+    // but we need to make sure that it is not used outside there; the
+    // compiler-provided version won't handle reference counting properly.
+    WebPrivatePtr<T>& operator=(const WebPrivatePtr<T>& other);
 #endif
+    // Disable copy; classes that contain a WebPrivatePtr should implement their

[darin (slow to review), 2013/05/22 20:28:22]

ditto: copy -> copy constructor

[dmichael (off chromium), 2013/05/22 20:54:29]

Done.

+    // copy constructor using assign().
+    WebPrivatePtr(const WebPrivatePtr<T>&);
 
     T* m_ptr;
 };
 
 } // namespace WebKit
 
 #endif