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

ash/wm/toplevel_window_event_handler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm/toplevel_window_event_handler.h"
 
 #include "ash/shell.h"
 #include "ash/wm/resize_shadow_controller.h"
 #include "ash/wm/window_resizer.h"
 #include "ash/wm/window_state.h"
@@ skipping 334 matching lines @@
   drag_reverted_ = (status == DRAG_REVERT);
 
   in_gesture_drag_ = false;
   if (in_move_loop_)
     quit_closure_.Run();
 }
 
 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
   // mouse-drag-release-press case, where the mouse is released and
   // pressed without mouse move event.
   int component =
       target->delegate()->GetNonClientComponent(event->location());
   if ((event->flags() &
         (ui::EF_IS_DOUBLE_CLICK | ui::EF_IS_TRIPLE_CLICK)) == 0 &&
       WindowResizer::GetBoundsChangeForWindowComponent(component)) {
@@ skipping 44 matching lines @@
       ConvertPointToParent(target, event->location()), event->flags());
   event->StopPropagation();
 }
 
 void ToplevelWindowEventHandler::HandleMouseMoved(
     aura::Window* target,
     ui::LocatedEvent* event) {
   // 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
   // CompoundEventFilter?
   internal::ResizeShadowController* controller =
       Shell::GetInstance()->resize_shadow_controller();
   if (controller) {
     if (event->flags() & ui::EF_IS_NON_CLIENT) {
       int component =
           target->delegate()->GetNonClientComponent(event->location());
@@ skipping 58 matching lines @@
 
 void ToplevelWindowEventHandler::ResizerWindowDestroyed() {
   // We explicitly don't invoke RevertDrag() since that may do things to window.
   // Instead we destroy the resizer.
   window_resizer_.reset();
 
   CompleteDrag(DRAG_REVERT);
 }
 
 }  // namespace ash