Improvements to WorkQueueThread

- Do not use a lambda for std::thread as invoke constructor exists
- Use simpler std::lock_guard wherever possible
- Do not require T to be default constructible
- Move T out of the queue instead of copying

Source/Core/Common/WorkQueueThread.h

@@ -27,14 +27,14 @@ public:
     Shutdown();
     m_shutdown.Clear();
     m_function = std::move(function);
-    m_thread = std::thread([this] { ThreadLoop(); });
+    m_thread = std::thread(&WorkQueueThread::ThreadLoop, this);
   }
 
   template <typename... Args>
   void EmplaceItem(Args&&... args)
   {
     {
-      std::unique_lock<std::mutex> lg(m_lock);
+      std::lock_guard lg(m_lock);
       m_items.emplace(std::forward<Args>(args)...);
     }
     m_wakeup.Set();
@@ -59,14 +59,13 @@ private:
 
       while (true)
       {
-        T item;
-        {
-          std::unique_lock<std::mutex> lg(m_lock);
-          if (m_items.empty())
-            break;
-          item = m_items.front();
-          m_items.pop();
-        }
+        std::unique_lock lg(m_lock);
+        if (m_items.empty())
+          break;
+        T item{std::move(m_items.front())};
+        m_items.pop();
+        lg.unlock();
+
         m_function(std::move(item));
       }