Explicitely pass ownership of ReadingListWebStateObserverUserDataWrapper

ios/chrome/browser/reading_list/reading_list_web_state_observer.mm

Index: ios/chrome/browser/reading_list/reading_list_web_state_observer.mm
diff --git a/ios/chrome/browser/reading_list/reading_list_web_state_observer.mm b/ios/chrome/browser/reading_list/reading_list_web_state_observer.mm
index c12abae78171eafa251ea9e0b5a0ec03647c861e..7c8a9fc926206fb6bcddaff038a96c4bc6727ecc 100644
--- a/ios/chrome/browser/reading_list/reading_list_web_state_observer.mm
+++ b/ios/chrome/browser/reading_list/reading_list_web_state_observer.mm
@@ -6,6 +6,7 @@
 
 #import <Foundation/Foundation.h>
 
+#include "base/memory/ptr_util.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/reading_list/reading_list_model.h"
 #include "ios/chrome/browser/reading_list/reading_list_model_factory.h"
@@ -34,8 +35,11 @@ class ReadingListWebStateObserverUserDataWrapper
         static_cast<ReadingListWebStateObserverUserDataWrapper*>(
             web_state->GetUserData(kObserverKey));
     if (!wrapper) {
-      wrapper = new ReadingListWebStateObserverUserDataWrapper(
-          web_state, reading_list_model);
+      auto newDataWrapper =

[sdefresne, 2016/11/22 10:01:31]

style: this is a C++ class, so the variable should use_cpp_naming_conventions.

On a higher level, most of the WebStateUserData inherits from
web::WebStateUserData (see ios/web/public/web_state/web_state_user_data.h).
Maybe this one should too.

I don't see when this object is created as
ReadingListWebStateObserver::FromWebState() seems to not yet be called (neither
upstream nor downstream) so I don't know if the lazily creation is a good model
for this object (i.e. code does not care whether this object exists before the
first interaction) but from its name it look like it may be interested in
capturing events as soon as the WebState is created.

If this is the case, then it is better to have an explicit construction (look
for CreateForWebState) and call it from the same location as the other
WebStateUserData (currently in downstream code).

+          base::MakeUnique<ReadingListWebStateObserverUserDataWrapper>(
+              web_state, reading_list_model);
+      wrapper = newDataWrapper.get();
+      web_state->SetUserData(kObserverKey, newDataWrapper.release());
     }
     return wrapper;
   }
@@ -45,7 +49,6 @@ class ReadingListWebStateObserverUserDataWrapper
       ReadingListModel* reading_list_model)
       : observer_(web_state, reading_list_model) {
     DCHECK(web_state);
-    web_state->SetUserData(kObserverKey, this);
   }
 
   ReadingListWebStateObserver* observer() { return &observer_; }