Add missing (and remove superfluous) 'explicit' from constructors.

jingle/glue/mock_task.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 mock of talk_base::Task.
 
 #ifndef JINGLE_GLUE_MOCK_TASK_H_
 #define JINGLE_GLUE_MOCK_TASK_H_
 
 #include "testing/gmock/include/gmock/gmock.h"
 #include "third_party/libjingle/source/talk/base/task.h"
 
 namespace jingle_glue {
 
 class MockTask : public talk_base::Task {
  public:
-  MockTask(TaskParent* parent);
+  explicit MockTask(TaskParent* parent);
 
   virtual ~MockTask();
 
   MOCK_METHOD0(ProcessStart, int());
 };
 
 }  // namespace jingle_glue
 
 #endif  // JINGLE_GLUE_MOCK_TASK_H_