Bug 1117977, make script load handling during shutdown safer, r=mccr8

--HG--
extra : rebase_source : d3f3b6961c97ae1a9b67e7b00f41247c1d67eea7

dom/base/nsScriptLoader.cpp

@@ -796,6 +796,8 @@ public:
     : mRequest(aRequest), mLoader(aLoader), mToken(nullptr)
   {}
 
+  virtual ~NotifyOffThreadScriptLoadCompletedRunnable();
+
   void SetToken(void* aToken) {
     MOZ_ASSERT(aToken && !mToken);
     mToken = aToken;
@@ -814,6 +816,23 @@ nsScriptLoader::ProcessOffThreadRequest(nsScriptLoadRequest* aRequest, void **aO
   return rv;
 }
 
+NotifyOffThreadScriptLoadCompletedRunnable::~NotifyOffThreadScriptLoadCompletedRunnable()
+{
+  if (MOZ_UNLIKELY(mRequest || mLoader) && !NS_IsMainThread()) {
+    nsCOMPtr<nsIThread> mainThread;
+    NS_GetMainThread(getter_AddRefs(mainThread));
+    if (mainThread) {
+      NS_ProxyRelease(mainThread, mRequest);
+      NS_ProxyRelease(mainThread, mLoader);
+    } else {
+      MOZ_ASSERT(false, "We really shouldn't leak!");
+      // Better to leak than crash.
+      unused << mRequest.forget();
+      unused << mLoader.forget();
+    }
+  }
+}
+
 NS_IMETHODIMP
 NotifyOffThreadScriptLoadCompletedRunnable::Run()
 {