Cleanup WebState and WebStateUserData API

ios/public/provider/web/web_state_user_data.h

 // Copyright 2013 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 IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
 #define IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_
 
-#include "ios/public/consumer/base/supports_user_data.h"
+#include "base/supports_user_data.h"
 #include "ios/public/provider/web/web_state.h"
 
 namespace ios {
 
 // A base class for classes attached to, and scoped to, the lifetime of a
 // WebState. For example:
 //
 // --- in foo.h ---
 // class Foo : public ios::WebStateUserData<Foo> {
 //  public:
 //   virtual ~Foo();
 //   // ... more public stuff here ...
 //  private:
 //   explicit Foo(ios::WebState* web_state);
 //   friend class ios::WebStateUserData<Foo>;
 //   // ... more private stuff here ...
 // }
 // --- in foo.cc ---
 // DEFINE_WEB_CONTENTS_USER_DATA_KEY(Foo);
 //
 template <typename T>
-class WebStateUserData : public ios::SupportsUserData::Data {
+class WebStateUserData : public base::SupportsUserData::Data {

[droger, 2014/12/04 09:39:47]

Important: This class needs a virtual destructor.

[sdefresne, 2014/12/05 14:32:05]

Done. But base::SupportsUserData::Data already has a virtual destructor and
since this class does not change anything, so AFAICT there is no need to
explicitly add a destructor there, right?

[droger, 2014/12/05 14:44:33]

I think there is a problem in this case, am I wrong?

class MyUserData : public WebStateUserData<MyUserData> {
  ...
};

WebStateUserData<MyUserData>* a = new MyUserData;
delete a;

Since the destructor is not virtual, it will not call the destructor of
MyUserData.

[droger, 2014/12/05 14:57:41]

Ok, it turns out I was wrong.
As long as the base class has a virtual destructor, all the subclasses are
implicitly virtual too.
Sorry about that.

  public:
   // Creates an object of type T, and attaches it to the specified WebState.
   // If an instance is already attached, does nothing.
   static void CreateForWebState(WebState* web_state) {
     if (!FromWebState(web_state))
       web_state->SetUserData(UserDataKey(), new T(web_state));
   }
 
   // Retrieves the instance of type T that was attached to the specified
   // WebState (via CreateForWebState above) and returns it. If no instance
@@ skipping 22 matching lines @@
 // a declaration. Without it, this would be merely a declaration of a template
 // specialization. (C++98: 14.7.3.15; C++11: 14.7.3.13)
 //
 #define DEFINE_WEB_STATE_USER_DATA_KEY(TYPE) \
 template<>                                      \
 int ios::WebStateUserData<TYPE>::kLocatorKey = 0
 
 }  // namespace ios
 
 #endif  // IOS_PUBLIC_PROVIDER_WEB_WEB_STATE_USER_DATA_H_