Draft change to use base::Closure instead of PrefObserver in PrefChangeRegistrar.

chrome/browser/api/prefs/pref_member.cc

Index: chrome/browser/api/prefs/pref_member.cc
diff --git a/chrome/browser/api/prefs/pref_member.cc b/chrome/browser/api/prefs/pref_member.cc
index e81b13a61081620b7495dbb94ac4f697fe0d344d..66bfa754158eedb98b95c09419ce823ce10212c5 100644
--- a/chrome/browser/api/prefs/pref_member.cc
+++ b/chrome/browser/api/prefs/pref_member.cc
@@ -4,7 +4,8 @@
 
 #include "chrome/browser/api/prefs/pref_member.h"
 
-#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
 #include "base/location.h"
 #include "base/prefs/public/pref_service_base.h"
 #include "base/value_conversions.h"
@@ -14,7 +15,7 @@ using base::MessageLoopProxy;
 namespace subtle {
 
 PrefMemberBase::PrefMemberBase()
-    : observer_(NULL),
+    : observer_(base::Bind(&base::DoNothing)),
       prefs_(NULL),
       setting_value_(false) {
 }
@@ -25,11 +26,16 @@ PrefMemberBase::~PrefMemberBase() {
 
 void PrefMemberBase::Init(const char* pref_name,
                           PrefServiceBase* prefs,
-                          PrefObserver* observer) {
+                          const base::Closure& observer) {
+  observer_ = observer;
+  Init(pref_name, prefs);
+}
+
+void PrefMemberBase::Init(const char* pref_name,
+                          PrefServiceBase* prefs) {
   DCHECK(pref_name);
   DCHECK(prefs);
   DCHECK(pref_name_.empty());  // Check that Init is only called once.
-  observer_ = observer;
   prefs_ = prefs;
   pref_name_ = pref_name;
   // Check that the preference is registered.
@@ -60,8 +66,8 @@ void PrefMemberBase::OnPreferenceChanged(PrefServiceBase* service,
                                          const std::string& pref_name) {
   VerifyValuePrefName();
   UpdateValueFromPref();
-  if (!setting_value_ && observer_)
-    observer_->OnPreferenceChanged(service, pref_name);
+  if (!setting_value_)
+    observer_.Run();
 }
 
 void PrefMemberBase::UpdateValueFromPref() const {