Bug 942040 - Remove a process from BackgroundProcessLRUPool in ParticularProcessPriorityManager only if it is indeed a background process. r=khuey

dom/ipc/ProcessPriorityManager.cpp

@@ -1045,7 +1045,9 @@ ParticularProcessPriorityManager::ShutDown()
     mResetPriorityTimer = nullptr;
   }
 
+  if (mPriority == PROCESS_PRIORITY_BACKGROUND && !IsPreallocated()) {
     ProcessPriorityManager::RemoveFromBackgroundLRUPool(mContentParent);
+  }
 
   mContentParent = nullptr;
 }