Make Mandoline shut down cleanly.

ui/platform_window/x11/x11_window.cc

Index: ui/platform_window/x11/x11_window.cc
diff --git a/ui/platform_window/x11/x11_window.cc b/ui/platform_window/x11/x11_window.cc
index 14e6fdf0b282421af5e88e7bf8c6c27032543337..57d3a5e20c47fb0f89adc9a95e261256ceb0aa66 100644
--- a/ui/platform_window/x11/x11_window.cc
+++ b/ui/platform_window/x11/x11_window.cc
@@ -52,18 +52,21 @@ X11Window::X11Window(PlatformWindowDelegate* delegate)
 }
 
 X11Window::~X11Window() {
-  Destroy();
 }
 
 void X11Window::Destroy() {
-  delegate_->OnClosed();
   if (xwindow_ == None)
     return;
 
   // Stop processing events.
   PlatformEventSource::GetInstance()->RemovePlatformEventDispatcher(this);
-  XDestroyWindow(xdisplay_, xwindow_);
+  XID xwindow = xwindow_;
+  XDisplay* xdisplay = xdisplay_;
   xwindow_ = None;
+  delegate_->OnClosed();
+  // |this| might be deleted because of the above call.
+
+  XDestroyWindow(xdisplay, xwindow);
 }
 
 void X11Window::ProcessXInput2Event(XEvent* xev) {