Revert of base: Remove use of MessageLoopProxy

base/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) {
@@ skipping 47 matching lines @@
     Internal();
 
     // Update the value, either by calling |UpdateValueInternal| directly
     // or by dispatching to the right thread.
     // Takes ownership of |value|.
     void UpdateValue(base::Value* value,
                      bool is_managed,
                      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 {
       return is_managed_;
     }
 
     bool IsUserModifiable() const {
       return is_user_modifiable_;
     }
 
    protected:
     friend class base::RefCountedThreadSafe<Internal>;
     virtual ~Internal();
 
     void CheckOnCorrectThread() const {
       DCHECK(IsOnCorrectThread());
     }
 
    private:
     // This method actually updates the value. It should only be called from
     // the thread the PrefMember is on.
     virtual bool UpdateValueInternal(const base::Value& value) const = 0;
 
     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_;
 
     DISALLOW_COPY_AND_ASSIGN(Internal);
   };
 
   PrefMemberBase();
   virtual ~PrefMemberBase();
 
   // See PrefMember<> for description.
   void Init(const std::string& pref_name,
             PrefService* prefs,
             const NamedChangeCallback& observer);
   void Init(const std::string& pref_name, PrefService* prefs);
 
   virtual void CreateInternal() const = 0;
 
   // 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,
                            const std::string& pref_name) override;
 
   void VerifyValuePrefName() const {
     DCHECK(!pref_name_.empty());
   }
 
   // This method is used to do the actual sync with the preference.
@@ skipping 66 matching lines @@
   // This method should only be called on the UI thread.
   void Destroy() {
     subtle::PrefMemberBase::Destroy();
   }
 
   // Moves the PrefMember to another thread, allowing read accesses from there.
   // Changes from the PrefService will be propagated asynchronously
   // 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);
   }
 
   // Check whether the pref is managed, i.e. controlled externally through
   // enterprise configuration management (e.g. windows group policy). Returns
   // false for unknown prefs.
   // This method should only be used from the thread the PrefMember is currently
   // on, which is the UI thread unless changed by |MoveToThread|.
   bool IsManaged() const {
     VerifyPref();
@@ skipping 133 matching lines @@
 
 typedef PrefMember<bool> BooleanPrefMember;
 typedef PrefMember<int> IntegerPrefMember;
 typedef PrefMember<double> DoublePrefMember;
 typedef PrefMember<std::string> StringPrefMember;
 typedef PrefMember<base::FilePath> FilePathPrefMember;
 // This preference member is expensive for large string arrays.
 typedef PrefMember<std::vector<std::string> > StringListPrefMember;
 
 #endif  // BASE_PREFS_PREF_MEMBER_H_