Bug 1330693 Try to handle SW job double-completion better. r=ehsan

dom/workers/ServiceWorkerJob.cpp

@@ -53,11 +53,11 @@ void
 ServiceWorkerJob::AppendResultCallback(Callback* aCallback)
 {
   AssertIsOnMainThread();
-  MOZ_ASSERT(mState != State::Finished);
-  MOZ_ASSERT(aCallback);
-  MOZ_ASSERT(mFinalCallback != aCallback);
+  MOZ_DIAGNOSTIC_ASSERT(mState != State::Finished);
+  MOZ_DIAGNOSTIC_ASSERT(aCallback);
+  MOZ_DIAGNOSTIC_ASSERT(mFinalCallback != aCallback);
   MOZ_ASSERT(!mResultCallbackList.Contains(aCallback));
-  MOZ_ASSERT(!mResultCallbacksInvoked);
+  MOZ_DIAGNOSTIC_ASSERT(!mResultCallbacksInvoked);
   mResultCallbackList.AppendElement(aCallback);
 }
 
@@ -84,14 +84,14 @@ void
 ServiceWorkerJob::Start(Callback* aFinalCallback)
 {
   AssertIsOnMainThread();
-  MOZ_ASSERT(!mCanceled);
+  MOZ_DIAGNOSTIC_ASSERT(!mCanceled);
 
-  MOZ_ASSERT(aFinalCallback);
-  MOZ_ASSERT(!mFinalCallback);
+  MOZ_DIAGNOSTIC_ASSERT(aFinalCallback);
+  MOZ_DIAGNOSTIC_ASSERT(!mFinalCallback);
   MOZ_ASSERT(!mResultCallbackList.Contains(aFinalCallback));
   mFinalCallback = aFinalCallback;
 
-  MOZ_ASSERT(mState == State::Initial);
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Initial);
   mState = State::Started;
 
   nsCOMPtr<nsIRunnable> runnable =
@@ -155,9 +155,9 @@ void
 ServiceWorkerJob::InvokeResultCallbacks(ErrorResult& aRv)
 {
   AssertIsOnMainThread();
-  MOZ_ASSERT(mState == State::Started);
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Started);
 
-  MOZ_ASSERT(!mResultCallbacksInvoked);
+  MOZ_DIAGNOSTIC_ASSERT(!mResultCallbacksInvoked);
   mResultCallbacksInvoked = true;
 
   nsTArray<RefPtr<Callback>> callbackList;
@@ -187,7 +187,14 @@ void
 ServiceWorkerJob::Finish(ErrorResult& aRv)
 {
   AssertIsOnMainThread();
-  MOZ_ASSERT(mState == State::Started);
+
+  // Avoid double-completion because it can result on operating on cleaned
+  // up data.  This should not happen, though, so also assert to try to
+  // narrow down the causes.
+  MOZ_DIAGNOSTIC_ASSERT(mState == State::Started);
+  if (mState != State::Started) {
+    return;
+  }
 
   // Ensure that we only surface SecurityErr, TypeErr or InvalidStateErr to script.
   if (aRv.Failed() && !aRv.ErrorCodeIs(NS_ERROR_DOM_SECURITY_ERR) &&
@@ -213,8 +220,11 @@ ServiceWorkerJob::Finish(ErrorResult& aRv)
 
   mState = State::Finished;
 
-  mFinalCallback->JobFinished(this, aRv);
-  mFinalCallback = nullptr;
+  MOZ_DIAGNOSTIC_ASSERT(mFinalCallback);
+  if (mFinalCallback) {
+    mFinalCallback->JobFinished(this, aRv);
+    mFinalCallback = nullptr;
+  }
 
   // The callback might not consume the error.
   aRv.SuppressException();