PVS-Studio warning V519 for Firefox

nsresult
PuppetWidget::DispatchPaintEvent()
{
  ...
  event.refPoint.x = dirtyRect.x;
  event.refPoint.x = dirtyRect.y;
  ...
}

This suspicious code was found in Firefox project by PVS-Studio static code analyzer.
Warning message is:
V519 The 'event.refPoint.x' variable is assigned values twice successively. Perhaps this is a mistake. Check lines: 545, 546. puppetwidget.cpp 546

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/