--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -50,16 +50,17 @@
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptSecurityManager.h"
 #include "nsPIDOMWindow.h"
 #include "nsITextToSubURI.h"
 #include "nsITimer.h"
 #include "nsIURI.h"
 #include "nsIURL.h"
 #include "nsIXPConnect.h"
+#include "nsIXPCScriptNotify.h"
 
 #include "jsfriendapi.h"
 #include "jsdbgapi.h"
 #include "jsfriendapi.h"
 #include "jsprf.h"
 #include "js/MemoryMetrics.h"
 #include "nsAlgorithm.h"
 #include "nsContentUtils.h"
@@ -961,16 +962,23 @@ public:
       CreateMessageEvent(aCx, buffer, mClonedObjects, mainRuntime);
     if (!event) {
       return false;
     }
 
     bool dummy;
     return DispatchEventToTarget(aCx, target, event, &dummy);
   }
+
+  void PostRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate, bool aRunResult)
+  {
+    // Notify before WorkerRunnable::PostRun, since that can kill aWorkerPrivate
+    NotifyScriptExecutedIfNeeded();
+    WorkerRunnable::PostRun(aCx, aWorkerPrivate, aRunResult);
+  }
 };
 
 class NotifyRunnable : public WorkerControlRunnable
 {
   bool mFromJSObjectFinalizer;
   Status mStatus;
 
 public:
@@ -1106,16 +1114,23 @@ public:
     }
 
     return ReportErrorRunnable::ReportError(aCx, parent, true, target, mMessage,
                                             mFilename, mLine, mLineNumber,
                                             mColumnNumber, mFlags,
                                             mErrorNumber, innerWindowId);
   }
 
+  void PostRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate, bool aRunResult)
+  {
+    // Notify before WorkerRunnable::PostRun, since that can kill aWorkerPrivate
+    NotifyScriptExecutedIfNeeded();
+    WorkerRunnable::PostRun(aCx, aWorkerPrivate, aRunResult);
+  }
+
   static bool
   ReportError(JSContext* aCx, WorkerPrivate* aWorkerPrivate,
               bool aFireAtScope, JSObject* aTarget, const nsString& aMessage,
               const nsString& aFilename, const nsString& aLine,
               PRUint32 aLineNumber, PRUint32 aColumnNumber, PRUint32 aFlags,
               PRUint32 aErrorNumber, PRUint64 aInnerWindowId)
   {
     if (aWorkerPrivate) {
@@ -1811,16 +1826,28 @@ WorkerRunnable::PostRun(JSContext* aCx, 
     }
   }
 
   if (!aRunResult) {
     JS_ReportPendingException(aCx);
   }
 }
 
+void
+WorkerRunnable::NotifyScriptExecutedIfNeeded() const
+{
+  // if we're on the main thread notify about the end of our script execution.
+  if (mTarget == ParentThread && !mWorkerPrivate->GetParent()) {
+    AssertIsOnMainThread();
+    if (mWorkerPrivate->GetScriptNotify()) {
+      mWorkerPrivate->GetScriptNotify()->ScriptExecuted();
+    }
+  }
+}
+
 struct WorkerPrivate::TimeoutInfo
 {
   TimeoutInfo()
   : mTimeoutVal(JSVAL_VOID), mLineNumber(0), mId(0), mIsInterval(false),
     mCanceled(false)
   {
     MOZ_COUNT_CTOR(mozilla::dom::workers::WorkerPrivate::TimeoutInfo);
   }
@@ -1876,16 +1903,17 @@ WorkerPrivateParent<Derived>::WorkerPriv
   MOZ_COUNT_CTOR(mozilla::dom::workers::WorkerPrivateParent);
 
   if (aWindow) {
     NS_ASSERTION(aWindow->IsInnerWindow(), "Should have inner window here!");
   }
 
   mWindow.swap(aWindow);
   mScriptContext.swap(aScriptContext);
+  mScriptNotify = do_QueryInterface(mScriptContext);
   mBaseURI.swap(aBaseURI);
   mPrincipal.swap(aPrincipal);
   mDocument.swap(aDocument);
 
   if (aParent) {
     aParent->AssertIsOnWorkerThread();
 
     NS_ASSERTION(JS_GetOptions(aCx) == aParent->GetJSContextOptions(),
@@ -2176,20 +2204,21 @@ WorkerPrivateParent<Derived>::RootJSObje
 template <class Derived>
 void
 WorkerPrivateParent<Derived>::ForgetMainThreadObjects(
                                       nsTArray<nsCOMPtr<nsISupports> >& aDoomed)
 {
   AssertIsOnParentThread();
   MOZ_ASSERT(!mMainThreadObjectsForgotten);
 
-  aDoomed.SetCapacity(6);
+  aDoomed.SetCapacity(7);
 
   SwapToISupportsArray(mWindow, aDoomed);
   SwapToISupportsArray(mScriptContext, aDoomed);
+  SwapToISupportsArray(mScriptNotify, aDoomed);
   SwapToISupportsArray(mBaseURI, aDoomed);
   SwapToISupportsArray(mScriptURI, aDoomed);
   SwapToISupportsArray(mPrincipal, aDoomed);
   SwapToISupportsArray(mDocument, aDoomed);
 
   mMainThreadObjectsForgotten = true;
 }
 

--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -64,16 +64,17 @@
 class JSAutoStructuredCloneBuffer;
 class nsIDocument;
 class nsIPrincipal;
 class nsIMemoryMultiReporter;
 class nsIScriptContext;
 class nsIURI;
 class nsPIDOMWindow;
 class nsITimer;
+class nsIXPCScriptNotify;
 
 BEGIN_WORKERS_NAMESPACE
 
 class WorkerPrivate;
 
 class WorkerRunnable : public nsIRunnable
 {
 public:
@@ -128,16 +129,18 @@ protected:
   DispatchInternal();
 
   virtual bool
   WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) = 0;
 
   virtual void
   PostRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate, bool aRunResult);
 
+  void NotifyScriptExecutedIfNeeded() const;
+
 private:
   NS_DECL_NSIRUNNABLE
 };
 
 class WorkerSyncRunnable : public WorkerRunnable
 {
 protected:
   PRUint32 mSyncQueueKey;
@@ -202,16 +205,17 @@ private:
   JSContext* mParentJSContext;
   nsString mScriptURL;
   nsCString mDomain;
   LocationInfo mLocationInfo;
 
   // Main-thread things.
   nsCOMPtr<nsPIDOMWindow> mWindow;
   nsCOMPtr<nsIScriptContext> mScriptContext;
+  nsCOMPtr<nsIXPCScriptNotify> mScriptNotify;
   nsCOMPtr<nsIURI> mBaseURI;
   nsCOMPtr<nsIURI> mScriptURI;
   nsCOMPtr<nsIPrincipal> mPrincipal;
   nsCOMPtr<nsIDocument> mDocument;
 
   // Only used for top level workers.
   nsTArray<nsRefPtr<WorkerRunnable> > mQueuedRunnables;
 
@@ -381,16 +385,23 @@ public:
 
   nsIScriptContext*
   GetScriptContext() const
   {
     AssertIsOnMainThread();
     return mScriptContext;
   }
 
+  nsIXPCScriptNotify*
+  GetScriptNotify() const
+  {
+    AssertIsOnMainThread();
+    return mScriptNotify;
+  }
+
   JSObject*
   GetJSObject() const
   {
     return mJSObject;
   }
 
   const nsString&
   ScriptURL() const