diff --git a/dom/media/MediaDecoder.cpp b/dom/media/MediaDecoder.cpp
index ba7bb30e86fd..ca9cc3d3eb52 100644
--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -659,19 +659,7 @@ bool
 MediaDecoder::IsExpectingMoreData()
 {
   ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
-
-  // If there's no resource, we're probably just getting set up.
-  if (!mResource) {
-    return true;
-  }
-
-  // If we've downloaded anything, we're not waiting for anything.
-  if (mResource->IsDataCachedToEndOfResource(mDecoderPosition)) {
-    return false;
-  }
-
-  // Otherwise, we should be getting data unless the stream is suspended.
-  return !mResource->IsSuspended();
+  return !mResource || mResource->IsExpectingMoreData();
 }
 
 void MediaDecoder::MetadataLoaded(nsAutoPtr<MediaInfo> aInfo,
diff --git a/dom/media/MediaResource.h b/dom/media/MediaResource.h
index 5f401d7b5c53..87d3794e8916 100644
--- a/dom/media/MediaResource.h
+++ b/dom/media/MediaResource.h
@@ -407,8 +407,9 @@ public:
   // an appendBuffer call on a MediaSource element.
   virtual bool IsExpectingMoreData()
   {
-    // TODO: return a sensible value for all sub-classes in next patch.
-    return false;
+    // MediaDecoder::mDecoderPosition is roughly the same as Tell() which
+    // returns a position updated by latest Read() or ReadAt().
+    return !IsDataCachedToEndOfResource(Tell()) && !IsSuspended();
   }
   // Returns true if this stream is suspended by the cache because the
   // cache is full. If true then the decoder should try to start consuming