Bug 1407243 - Don't immediately fire canplaythrough for infinite/live streams. r=jwwang

MozReview-Commit-ID: 2LQFa8PHvO5

--HG--
extra : rebase_source : 3534a963202658870221fca9cc238185d7e55156

dom/media/mediasource/MediaSourceDecoder.cpp

@@ -310,11 +310,7 @@ MediaSourceDecoder::CanPlayThroughImpl()
   }
   TimeUnit duration = TimeUnit::FromSeconds(mMediaSource->Duration());
   auto currentPosition = CurrentPosition();
-  if (duration.IsInfinite()) {
-    // We can't make an informed decision and just assume that it's a live
-    // stream
-    return true;
-  } else if (duration <= currentPosition) {
+  if (duration <= currentPosition) {
     return true;
   }
   // If we have data up to the mediasource's duration or 10s ahead, we can