MediaSource must use ref-counting to handle pending activity counting.

Source/modules/mediasource/MediaSource.cpp

Index: Source/modules/mediasource/MediaSource.cpp
diff --git a/Source/modules/mediasource/MediaSource.cpp b/Source/modules/mediasource/MediaSource.cpp
index 2efbc3eb0cd54588fb4ecd5cef3b24fb37d257fb..aa0a295c25867c84b0cc201706fd769ca934c6a0 100644
--- a/Source/modules/mediasource/MediaSource.cpp
+++ b/Source/modules/mediasource/MediaSource.cpp
@@ -89,7 +89,7 @@ const AtomicString& MediaSource::endedKeyword()
 
 MediaSource* MediaSource::create(ExecutionContext* context)
 {
-    MediaSource* mediaSource(adoptRefCountedGarbageCollectedWillBeNoop(new MediaSource(context)));
+    MediaSource* mediaSource(adoptRefCountedGarbageCollected(new MediaSource(context)));
     mediaSource->suspendIfNeeded();
     return mediaSource;
 }