Bug 1395017. P2 - assert ResourceStreamIterator should either run in the main thread or with the lock held. r=cpearce

MozReview-Commit-ID: Jm9alyQFFtA

--HG--
extra : rebase_source : 7e9c880d6d1f30440ea1ddb65db57b0d6503c186
extra : intermediate-source : d30bc071a565283823be5fbd27c59da0242e8c18
extra : source : 1f69aab306347acce8e4d927c6315658a8af7a3b

dom/media/MediaCache.cpp

@@ -234,6 +234,9 @@ public:
       , mResourceID(aResourceID)
       , mNext(0)
     {
+      MOZ_ASSERT(
+        NS_IsMainThread() ||
+        (aMediaCache->GetReentrantMonitor().AssertCurrentThreadIn(), true));
     }
     MediaCacheStream* Next()
     {