Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/api/prefs/pref_member.h

 // Copyright (c) 2012 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.
 //
 // A helper class that stays in sync with a preference (bool, int, real,
 // string or filepath).  For example:
 //
 // class MyClass {
 //  public:
 //   MyClass(PrefService* prefs) {
 //     my_string_.Init(prefs::kHomePage, prefs, NULL /* no observer */);

[Mattias Nissler (ping if slow), 2012/12/04 10:10:34]

Update this?

[Jói, 2012/12/04 10:55:57]

Done.

 //   }
 //  private:
 //   StringPrefMember my_string_;
 // };
 //
 // my_string_ should stay in sync with the prefs::kHomePage pref and will
 // update if either the pref changes or if my_string_.SetValue is called.
 //
 // An optional observer can be passed into the Init method which can be used to
 // notify MyClass of changes. Note that if you use SetValue(), the observer
@@ skipping 74 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(Internal);
   };
 
   PrefMemberBase();
   virtual ~PrefMemberBase();
 
   // See PrefMember<> for description.
   void Init(const char* pref_name, PrefServiceBase* prefs,
             const NamedChangeCallback& observer);
+  void Init(const char* pref_name, PrefServiceBase* prefs);

[Mattias Nissler (ping if slow), 2012/12/04 10:10:34]

So this wasn't used previously? ;)

Any reason to expose this? Can't we just have the consumer below pass a
NamedChangeCallback() as before?

[Jói, 2012/12/04 10:55:57]

It's a performance optimization; we already create a do-nothing
NamedChangeCallback in the constructor of PrefMemberBase, no need to do it
again.

[Mattias Nissler (ping if slow), 2012/12/04 11:18:33]

Is the difference measurable? I usually prefer less/simpler code over premature
optimizations :)

[Jói, 2012/12/04 11:42:26]

The performance difference is probably not measurable except by a targeted
microbenchmark.  OTOH, I don't really feel this version of the code is more
complex, and it avoids some unnecessary work.  Up to you, let me know if you
prefer I get rid of the two-parameter PrefMemberBase::Init.

[Mattias Nissler (ping if slow), 2012/12/04 15:24:37]

I don't feel too strong, feel free to keep as is.

 
   virtual void CreateInternal() const = 0;
 
   // See PrefMember<> for description.
   void Destroy();
 
   void MoveToThread(const scoped_refptr<base::MessageLoopProxy>& message_loop);
 
   // PrefObserver
   virtual void OnPreferenceChanged(PrefServiceBase* service,
@@ skipping 55 matching lines @@
   void Init(const char* pref_name, PrefServiceBase* prefs,
             const base::Closure& observer) {
     subtle::PrefMemberBase::Init(
         pref_name, prefs,
         base::Bind(&PrefMemberBase::InvokeUnnamedCallback, observer));
   }
   void Init(const char* pref_name, PrefServiceBase* prefs) {
     subtle::PrefMemberBase::Init(pref_name, prefs);
   }
 
-  // Deprecated version of Init.
-  void Init(const char* pref_name, PrefServiceBase* prefs,
-            PrefObserver* observer) {
-    if (observer) {
-      Init(pref_name, prefs, base::Bind(&PrefObserver::OnPreferenceChanged,
-                                        base::Unretained(observer), prefs));
-    } else {
-      Init(pref_name, prefs, NamedChangeCallback());
-    }
-  }
-
   // Unsubscribes the PrefMember from the PrefService. After calling this
   // function, the PrefMember may not be used any more on the UI thread.
   // Assuming |MoveToThread| was previously called, |GetValue|, |IsManaged|,
   // and |IsUserModifiable| can still be called from the other thread but
   // the results will no longer update from the PrefService.
   // This method should only be called on the UI thread.
   void Destroy() {
     subtle::PrefMemberBase::Destroy();
   }
 
@@ skipping 90 matching lines @@
 
 typedef PrefMember<bool> BooleanPrefMember;
 typedef PrefMember<int> IntegerPrefMember;
 typedef PrefMember<double> DoublePrefMember;
 typedef PrefMember<std::string> StringPrefMember;
 typedef PrefMember<FilePath> FilePathPrefMember;
 // This preference member is expensive for large string arrays.
 typedef PrefMember<std::vector<std::string> > StringListPrefMember;
 
 #endif  // CHROME_BROWSER_API_PREFS_PREF_MEMBER_H_