From 8df5d9263aa535386e3624120ca75886d05bc84a Mon Sep 17 00:00:00 2001
From: Ben Kelly <ben@wanderview.com>
Date: Mon, 12 Sep 2016 06:09:32 -0700
Subject: [PATCH] Bug 1301519 Don't crash if GetCurrentThreadWorkerPrivate() is
 called during worker shutdown. r=baku

---
 dom/workers/RuntimeService.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
index 1f53b4695d0a..8e16a601dacc 100644
--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -1437,7 +1437,9 @@ GetWorkerPrivateFromContext(JSContext* aCx)
   MOZ_ASSERT(aCx);
 
   void* cxPrivate = JS_GetContextPrivate(aCx);
-  MOZ_ASSERT(cxPrivate);
+  if (!cxPrivate) {
+    return nullptr;
+  }
 
   return
     static_cast<WorkerThreadContextPrivate*>(cxPrivate)->GetWorkerPrivate();
@@ -1457,7 +1459,13 @@ GetCurrentThreadWorkerPrivate()
   MOZ_ASSERT(cx);
 
   void* cxPrivate = JS_GetContextPrivate(cx);
-  MOZ_ASSERT(cxPrivate);
+  if (!cxPrivate) {
+    // This can happen if the nsCycleCollector_shutdown() in ~WorkerJSRuntime()
+    // triggers any calls to GetCurrentThreadWorkerPrivate().  At this stage
+    // CycleCollectedJSRuntime::Get() will still return a runtime, but
+    // the context private has already been cleared.
+    return nullptr;
+  }
 
   return
     static_cast<WorkerThreadContextPrivate*>(cxPrivate)->GetWorkerPrivate();