fix build when ffmpeg, libvpx and libwebm are disabled

chrome/utility/media_galleries/media_metadata_parser.cc

Index: chrome/utility/media_galleries/media_metadata_parser.cc
diff --git a/chrome/utility/media_galleries/media_metadata_parser.cc b/chrome/utility/media_galleries/media_metadata_parser.cc
index b1fb81c53203784c1b1894c7a3f4e4b98e59bc9b..3d6e733149318678911d4d85634434a97dde97e3 100644
--- a/chrome/utility/media_galleries/media_metadata_parser.cc
+++ b/chrome/utility/media_galleries/media_metadata_parser.cc
@@ -56,6 +56,8 @@ void ParseAudioVideoMetadata(
     std::vector<AttachedImage>* attached_images) {
   DCHECK(source);
   DCHECK(metadata);
+
+#if !defined(MEDIA_DISABLE_FFMPEG)
   media::AudioVideoMetadataExtractor extractor;
 
   if (!extractor.Extract(source, get_attached_images))
@@ -108,6 +110,7 @@ void ParseAudioVideoMetadata(
                                       &attached_images->back().type);
     }
   }
+#endif
 }
 
 void FinishParseAudioVideoMetadata(