message: Improve conhost CPU usage during text selection
diff: @@ -255,6 +255,14 @@ void Selection::ExtendSelection(_In_ COORD coordBufferPos)
  srNewSelection.Top = _coordSelectionAnchor.Y;
  }
  + // This function is called on WM_MOUSEMOVE.
  + // Prevent triggering an invalidation just because the mouse moved
  + // in the same cell without changing the actual (visible) selection.
  + if (_srSelectionRect == srNewSelection)
  + {
  + return;
  + }
  +
  // call special update method to modify the displayed selection in-place
  // NOTE: Using HideSelection, editing the rectangle, then ShowSelection will cause flicker.
  //_PaintUpdateSelection(&srNewSelection);
  