Revert of base: Remove use of MessageLoopProxy

base/prefs/pref_member.h

Index: base/prefs/pref_member.h
diff --git a/base/prefs/pref_member.h b/base/prefs/pref_member.h
index 6dceb439ed76c8d97bd5a745443a1569ff99e901..9b140d16748e7ea5516687ea9ab9b514452c1c84 100644
--- a/base/prefs/pref_member.h
+++ b/base/prefs/pref_member.h
@@ -65,7 +65,8 @@
                      bool is_user_modifiable,
                      const base::Closure& callback) const;
 
-    void MoveToThread(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+    void MoveToThread(
+        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
 
     // See PrefMember<> for description.
     bool IsManaged() const {
@@ -91,7 +92,7 @@
 
     bool IsOnCorrectThread() const;
 
-    scoped_refptr<base::SingleThreadTaskRunner> thread_task_runner_;
+    scoped_refptr<base::SingleThreadTaskRunner> thread_loop_;
     mutable bool is_managed_;
     mutable bool is_user_modifiable_;
 
@@ -112,7 +113,8 @@
   // See PrefMember<> for description.
   void Destroy();
 
-  void MoveToThread(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  void MoveToThread(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
 
   // PrefObserver
   void OnPreferenceChanged(PrefService* service,
@@ -199,7 +201,8 @@
   // via PostTask.
   // This method should only be used from the thread the PrefMember is currently
   // on, which is the UI thread by default.
-  void MoveToThread(scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  void MoveToThread(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
     subtle::PrefMemberBase::MoveToThread(task_runner);
   }