MSE: Increase log visibility when unfragmented MP4 causes parse failure

media/formats/mp4/box_reader.cc

Index: media/formats/mp4/box_reader.cc
diff --git a/media/formats/mp4/box_reader.cc b/media/formats/mp4/box_reader.cc
index edebddd1a7fd180c45df3fabe52a1843f26e38d2..5105726da5d23ba2dddfbbc0469f2bacfd156b73 100644
--- a/media/formats/mp4/box_reader.cc
+++ b/media/formats/mp4/box_reader.cc
@@ -219,7 +219,8 @@ bool BoxReader::ReadHeader(bool* err) {
   CHECK(Read4Into8(&size) && ReadFourCC(&type_));
 
   if (size == 0) {
-    // Media Source specific: we do not support boxes that run to EOS.
+    MEDIA_LOG(DEBUG, log_cb_) << "Media Source Extensions do not support ISO "
+                                 "BMFF boxes that run to EOS";
     *err = true;
     return false;
   } else if (size == 1) {