Convert MediaLog from being ref counted to owned by WebMediaPlayer.

media/base/media_log.cc

Index: media/base/media_log.cc
diff --git a/media/base/media_log.cc b/media/base/media_log.cc
index e354ea03e8c05115636a2a9d0d2e9c759ee63ac9..76b6b40db3326e837af5f9ab8867e4a6130ee1ce 100644
--- a/media/base/media_log.cc
+++ b/media/base/media_log.cc
@@ -378,10 +378,9 @@ void MediaLog::SetBooleanProperty(
   AddEvent(std::move(event));
 }
 
-LogHelper::LogHelper(MediaLog::MediaLogLevel level,
-                     const scoped_refptr<MediaLog>& media_log)
+LogHelper::LogHelper(MediaLog::MediaLogLevel level, MediaLog* media_log)
     : level_(level), media_log_(media_log) {
-  DCHECK(media_log_.get());
+  DCHECK(media_log_);
 }
 
 LogHelper::~LogHelper() {