Bug 1733109 - narrowing conversion from 'unsigned long' to signed type 'int32_t' (aka 'int') is implementation-defined HTMLMediaElement.cpp. r=pehrsons

Somewhat controversial, let me know what you think.

Differential Revision: https://phabricator.services.mozilla.com/D126939

dom/html/HTMLMediaElement.cpp

@@ -3645,7 +3645,7 @@ void HTMLMediaElement::UpdateOutputTrackSources() {
   }
 
   // Then update finish-when-ended output streams as needed.
-  for (int32_t i = mOutputStreams.Length() - 1; i >= 0; --i) {
+  for (size_t i = mOutputStreams.Length(); i-- > 0;) {
     if (!mOutputStreams[i].mFinishWhenEnded) {
       continue;
     }