Fixes for re-enabling more MSVC level 4 warnings: media/ edition

media/base/audio_video_metadata_extractor.cc

Index: media/base/audio_video_metadata_extractor.cc
diff --git a/media/base/audio_video_metadata_extractor.cc b/media/base/audio_video_metadata_extractor.cc
index 7a8cf766abde16b92d10c4f03647682eaf02a40d..fd666f6c919448ccd386a91e702fa1d9fc5ba101 100644
--- a/media/base/audio_video_metadata_extractor.cc
+++ b/media/base/audio_video_metadata_extractor.cc
@@ -236,8 +236,9 @@ void AudioVideoMetadataExtractor::ExtractDictionary(
   if (!metadata)
     return;
 
-  AVDictionaryEntry* tag = NULL;
-  while ((tag = av_dict_get(metadata, "", tag, AV_DICT_IGNORE_SUFFIX))) {
+  for (AVDictionaryEntry* tag =
+           av_dict_get(metadata, "", NULL, AV_DICT_IGNORE_SUFFIX);
+       tag; tag = av_dict_get(metadata, "", tag, AV_DICT_IGNORE_SUFFIX)) {
     if (raw_tags->find(tag->key) == raw_tags->end())
       (*raw_tags)[tag->key] = tag->value;