Check WindowDelegate in the methods which assume the target has the delegate.

ash/wm/toplevel_window_event_handler.cc

Index: ash/wm/toplevel_window_event_handler.cc
diff --git a/ash/wm/toplevel_window_event_handler.cc b/ash/wm/toplevel_window_event_handler.cc
index 635860f356cf633efd1c0d37e74e688f5af6313b..264ceb5e6cb66110d352812daa056cec6075545b 100644
--- a/ash/wm/toplevel_window_event_handler.cc
+++ b/ash/wm/toplevel_window_event_handler.cc
@@ -352,7 +352,7 @@ void ToplevelWindowEventHandler::CompleteDrag(DragCompletionStatus status) {
 void ToplevelWindowEventHandler::HandleMousePressed(
     aura::Window* target,
     ui::MouseEvent* event) {
-  if (event->phase() != ui::EP_PRETARGET)
+  if (event->phase() != ui::EP_PRETARGET || !target->delegate())
     return;
 
   // We also update the current window component here because for the
@@ -417,7 +417,7 @@ void ToplevelWindowEventHandler::HandleMouseMoved(
   // Shadow effects are applied after target handling. Note that we don't
   // respect ER_HANDLED here right now since we have not had a reason to allow
   // the target to cancel shadow rendering.
-  if (event->phase() != ui::EP_POSTTARGET)
+  if (event->phase() != ui::EP_POSTTARGET || !target->delegate())
     return;
 
   // TODO(jamescook): Move the resize cursor update code into here from