--- a/dom/ipc/jsactor/JSActor.cpp
+++ b/dom/ipc/jsactor/JSActor.cpp
@@ -65,17 +65,18 @@ void JSActor::StartDestroy() {
 void JSActor::AfterDestroy() {
   mCanSend = false;
 
   // Take our queries out, in case somehow rejecting promises can trigger
   // additions or removals.
   nsRefPtrHashtable<nsUint64HashKey, Promise> pendingQueries;
   mPendingQueries.SwapElements(pendingQueries);
   for (auto& entry : pendingQueries) {
-    entry.GetData()->MaybeReject(NS_ERROR_NOT_AVAILABLE);
+    entry.GetData()->MaybeRejectWithAbortError(nsPrintfCString(
+        "Actor '%s' destroyed before query was resolved", mName.get()));
   }
 
   InvokeCallback(CallbackFunction::DidDestroy);
   ClearManager();
 }
 
 void JSActor::InvokeCallback(CallbackFunction callback) {
   MOZ_ASSERT(nsContentUtils::IsSafeToRunScript());
@@ -187,17 +188,19 @@ static ipc::StructuredCloneData CaptureJ
   return CloneJSStack(aCx, stack);
 }
 
 void JSActor::SendAsyncMessage(JSContext* aCx, const nsAString& aMessageName,
                                JS::Handle<JS::Value> aObj, ErrorResult& aRv) {
   ipc::StructuredCloneData data;
   if (!nsFrameMessageManager::GetParamsForMessage(
           aCx, aObj, JS::UndefinedHandleValue, data)) {
-    aRv.Throw(NS_ERROR_DOM_DATA_CLONE_ERR);
+    aRv.ThrowDataCloneError(nsPrintfCString(
+        "Failed to serialize message '%s::%s'",
+        NS_LossyConvertUTF16toASCII(aMessageName).get(), mName.get()));
     return;
   }
 
   JSActorMessageMeta meta;
   meta.actorName() = mName;
   meta.messageName() = aMessageName;
   meta.kind() = JSActorMessageKind::Message;
 
@@ -206,23 +209,25 @@ void JSActor::SendAsyncMessage(JSContext
 
 already_AddRefed<Promise> JSActor::SendQuery(JSContext* aCx,
                                              const nsAString& aMessageName,
                                              JS::Handle<JS::Value> aObj,
                                              ErrorResult& aRv) {
   ipc::StructuredCloneData data;
   if (!nsFrameMessageManager::GetParamsForMessage(
           aCx, aObj, JS::UndefinedHandleValue, data)) {
-    aRv.Throw(NS_ERROR_DOM_DATA_CLONE_ERR);
+    aRv.ThrowDataCloneError(nsPrintfCString(
+        "Failed to serialize message '%s::%s'",
+        NS_LossyConvertUTF16toASCII(aMessageName).get(), mName.get()));
     return nullptr;
   }
 
   nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
   if (NS_WARN_IF(!global)) {
-    aRv.Throw(NS_ERROR_UNEXPECTED);
+    aRv.ThrowUnknownError("Unable to get current native global");
     return nullptr;
   }
 
   RefPtr<Promise> promise = Promise::Create(global, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
 
@@ -290,31 +295,31 @@ void JSActor::ReceiveMessageOrQuery(JSCo
     }
   }
 }
 
 void JSActor::ReceiveQueryReply(JSContext* aCx,
                                 const JSActorMessageMeta& aMetadata,
                                 JS::Handle<JS::Value> aData, ErrorResult& aRv) {
   if (NS_WARN_IF(aMetadata.actorName() != mName)) {
-    aRv.Throw(NS_ERROR_UNEXPECTED);
+    aRv.ThrowUnknownError("Mismatched actor name for query reply");
     return;
   }
 
   RefPtr<Promise> promise;
   if (NS_WARN_IF(!mPendingQueries.Remove(aMetadata.queryId(),
                                          getter_AddRefs(promise)))) {
-    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    aRv.ThrowUnknownError("Received reply for non-pending query");
     return;
   }
 
   JSAutoRealm ar(aCx, promise->PromiseObj());
   JS::RootedValue data(aCx, aData);
   if (NS_WARN_IF(!JS_WrapValue(aCx, &data))) {
-    aRv.Throw(NS_ERROR_FAILURE);
+    aRv.NoteJSContextException(aCx);
     return;
   }
 
   if (aMetadata.kind() == JSActorMessageKind::QueryResolve) {
     promise->MaybeResolve(data);
   } else {
     promise->MaybeReject(data);
   }