add default constructor to PendingTask; compilation fix for VS2012

base/pending_task.h

 // Copyright (c) 2011 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 PENDING_TASK_H_
 #define PENDING_TASK_H_
 
 #include <queue>
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/time.h"
 #include "base/tracking_info.h"
 
 namespace base {
 
 // Contains data about a pending task. Stored in TaskQueue and DelayedTaskQueue
 // for use by classes that queue and execute tasks.
 struct BASE_EXPORT PendingTask : public TrackingInfo {
+  PendingTask();
   PendingTask(const tracked_objects::Location& posted_from,
               const Closure& task);
   PendingTask(const tracked_objects::Location& posted_from,
               const Closure& task,
               TimeTicks delayed_run_time,
               bool nestable);
   ~PendingTask();
 
   // Used to support sorting.
   bool operator<(const PendingTask& other) const;
@@ skipping 17 matching lines @@
  public:
   void Swap(TaskQueue* queue);
 };
 
 // PendingTasks are sorted by their |delayed_run_time| property.
 typedef std::priority_queue<base::PendingTask> DelayedTaskQueue;
 
 }  // namespace base
 
 #endif  // PENDING_TASK_H_