Temporarily reverted main thread delays to the old way to reduce CPU usage until we figure out a better way that gives more accuracy at comparably reduced CPU usage.

src/qt/qt_main.cpp

@@ -120,10 +120,7 @@ main_thread_fn()
             }
         } else {
             /* Just so we dont overload the host OS. */
-            if (drawits < -1 || dopause)
-                std::this_thread::sleep_for(std::chrono::milliseconds(1));
-            else
-                std::this_thread::yield();
+            std::this_thread::sleep_for(std::chrono::milliseconds(1));
         }
 
         /* If needed, handle a screen resize. */