Revert of base: Remove use of MessageLoopProxy

base/observer_list_threadsafe.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.
 
 #ifndef BASE_OBSERVER_LIST_THREADSAFE_H_
 #define BASE_OBSERVER_LIST_THREADSAFE_H_
 
 #include <algorithm>
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
 #include "base/observer_list.h"
-#include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
-#include "base/thread_task_runner_handle.h"
 #include "base/threading/platform_thread.h"
 
 ///////////////////////////////////////////////////////////////////////////////
 //
 // OVERVIEW:
 //
 //   A thread-safe container for a list of observers.
 //   This is similar to the observer_list (see observer_list.h), but it
 //   is more robust for multi-threaded situations.
 //
@@ skipping 140 matching lines @@
   template <class Method, class... Params>
   void Notify(const tracked_objects::Location& from_here,
               Method m,
               const Params&... params) {
     UnboundMethod<ObserverType, Method, Tuple<Params...>> method(
         m, MakeTuple(params...));
 
     base::AutoLock lock(list_lock_);
     for (const auto& entry : observer_lists_) {
       ObserverListContext* context = entry.second;
-      context->task_runner->PostTask(
+      context->loop->PostTask(
           from_here,
           base::Bind(
               &ObserverListThreadSafe<ObserverType>::template NotifyWrapper<
                   Method, Tuple<Params...>>,
               this, context, method));
     }
   }
 
  private:
   // See comment above ObserverListThreadSafeTraits' definition.
   friend struct ObserverListThreadSafeTraits<ObserverType>;
 
   struct ObserverListContext {
     explicit ObserverListContext(NotificationType type)
-        : task_runner(base::ThreadTaskRunnerHandle::Get()), list(type) {}
+        : loop(base::MessageLoopProxy::current()),
+          list(type) {
+    }
 
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner;
+    scoped_refptr<base::MessageLoopProxy> loop;
     ObserverList<ObserverType> list;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ObserverListContext);
   };
 
   ~ObserverListThreadSafe() {
     STLDeleteValues(&observer_lists_);
   }
 
@@ skipping 47 matching lines @@
       ObserversListMap;
 
   mutable base::Lock list_lock_;  // Protects the observer_lists_.
   ObserversListMap observer_lists_;
   const NotificationType type_;
 
   DISALLOW_COPY_AND_ASSIGN(ObserverListThreadSafe);
 };
 
 #endif  // BASE_OBSERVER_LIST_THREADSAFE_H_