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

media/base/media_log.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 MEDIA_BASE_MEDIA_LOG_H_
 #define MEDIA_BASE_MEDIA_LOG_H_
 
 #include <sstream>
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 #include "media/base/media_log_event.h"
 #include "media/base/pipeline.h"
 #include "media/base/pipeline_status.h"
 
 namespace media {
 
 // Indicates a string should be added to the log.
 // First parameter - The string to add to the log.
 typedef base::Callback<void(const std::string&)> LogCB;
 
 // Helper class to make it easier to use log_cb like DVLOG().
 class LogHelper {
  public:
-  LogHelper(const LogCB& Log_cb);
+  explicit LogHelper(const LogCB& Log_cb);
   ~LogHelper();
 
   std::ostream& stream() { return stream_; }
 
  private:
   LogCB log_cb_;
   std::stringstream stream_;
 };
 
 #define MEDIA_LOG(log_cb) LogHelper(log_cb).stream()
@@ skipping 37 matching lines @@
  private:
   // A unique (to this process) id for this MediaLog.
   int32 id_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaLog);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_MEDIA_LOG_H_