Bug 1379243 P2 Fix some spurious warnings in WorkerPrivate. r=baku

dom/workers/WorkerPrivate.cpp

@@ -5051,7 +5051,7 @@ WorkerPrivate::DoRunLoop(JSContext* aCx)
         // After mStatus is set to Dead there can be no more
         // WorkerControlRunnables so no need to lock here.
         if (!mControlQueue.IsEmpty()) {
-          WorkerControlRunnable* runnable;
+          WorkerControlRunnable* runnable = nullptr;
           while (mControlQueue.Pop(runnable)) {
             runnable->Cancel();
             runnable->Release();
@@ -5072,7 +5072,7 @@ WorkerPrivate::DoRunLoop(JSContext* aCx)
     }
 
     if (debuggerRunnablesPending) {
-      WorkerRunnable* runnable;
+      WorkerRunnable* runnable = nullptr;
 
       {
         MutexAutoLock lock(mMutex);
@@ -5521,7 +5521,7 @@ void
 WorkerPrivate::ClearDebuggerEventQueue()
 {
   while (!mDebuggerQueue.IsEmpty()) {
-    WorkerRunnable* runnable;
+    WorkerRunnable* runnable = nullptr;
     mDebuggerQueue.Pop(runnable);
     // It should be ok to simply release the runnable, without running it.
     runnable->Release();
@@ -6071,7 +6071,7 @@ WorkerPrivate::EnterDebuggerEventLoop()
       // Start the periodic GC timer if it is not already running.
       SetGCTimerMode(PeriodicTimer);
 
-      WorkerRunnable* runnable;
+      WorkerRunnable* runnable = nullptr;
 
       {
         MutexAutoLock lock(mMutex);