--- a/content/media/DecoderTraits.cpp
+++ b/content/media/DecoderTraits.cpp
@@ -482,16 +482,22 @@ DecoderTraits::CanHandleMediaType(const 
 
 // Instantiates but does not initialize decoder.
 static
 already_AddRefed<MediaDecoder>
 InstantiateDecoder(const nsACString& aType, MediaDecoderOwner* aOwner)
 {
   nsRefPtr<MediaDecoder> decoder;
 
+#ifdef MOZ_FMP4
+  if (IsMP4SupportedType(aType)) {
+    decoder = new MP4Decoder();
+    return decoder.forget();
+  }
+#endif
 #ifdef MOZ_GSTREAMER
   if (IsGStreamerSupportedType(aType)) {
     decoder = new GStreamerDecoder();
     return decoder.forget();
   }
 #endif
 #ifdef MOZ_RAW
   if (IsRawType(aType)) {
@@ -552,22 +558,16 @@ InstantiateDecoder(const nsACString& aTy
 #ifdef MOZ_DIRECTSHOW
   // Note: DirectShow should come before WMF, so that we prefer DirectShow's
   // MP3 support over WMF's.
   if (IsDirectShowSupportedType(aType)) {
     decoder = new DirectShowDecoder();
     return decoder.forget();
   }
 #endif
-#ifdef MOZ_FMP4
-  if (IsMP4SupportedType(aType)) {
-    decoder = new MP4Decoder();
-    return decoder.forget();
-  }
-#endif
 #ifdef MOZ_WMF
   if (IsWMFSupportedType(aType)) {
     decoder = new WMFDecoder();
     return decoder.forget();
   }
 #endif
 #ifdef MOZ_APPLEMEDIA
   if (IsAppleMediaSupportedType(aType)) {
@@ -592,16 +592,21 @@ DecoderTraits::CreateDecoder(const nsACS
   return decoder.forget();
 }
 
 /* static */
 MediaDecoderReader* DecoderTraits::CreateReader(const nsACString& aType, AbstractMediaDecoder* aDecoder)
 {
   MediaDecoderReader* decoderReader = nullptr;
 
+#ifdef MOZ_FMP4
+  if (IsMP4SupportedType(aType)) {
+    decoderReader = new MP4Reader(aDecoder);
+  } else
+#endif
 #ifdef MOZ_GSTREAMER
   if (IsGStreamerSupportedType(aType)) {
     decoderReader = new GStreamerReader(aDecoder);
   } else
 #endif
 #ifdef MOZ_RAW
   if (IsRawType(aType)) {
     decoderReader = new RawReader(aDecoder);
@@ -633,21 +638,16 @@ MediaDecoderReader* DecoderTraits::Creat
 #endif
 #ifdef MOZ_DIRECTSHOW
   // Note: DirectShowReader is preferred for MP3, but if it's disabled we
   // fallback to the WMFReader.
   if (IsDirectShowSupportedType(aType)) {
     decoderReader = new DirectShowReader(aDecoder);
   } else
 #endif
-#ifdef MOZ_FMP4
-  if (IsMP4SupportedType(aType)) {
-    decoderReader = new MP4Reader(aDecoder);
-  } else
-#endif
 #ifdef MOZ_WMF
   if (IsWMFSupportedType(aType)) {
     decoderReader = new WMFReader(aDecoder);
   } else
 #endif
 #ifdef MOZ_APPLEMEDIA
   if (IsAppleMediaSupportedType(aType)) {
     decoderReader = new AppleMP3Reader(aDecoder);