Fixes a crash when InkDropDelegate gets destroyed after its InkDropHost

ui/views/controls/button/custom_button.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 "ui/views/controls/button/custom_button.h"
 
 #include "ui/accessibility/ax_view_state.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
 #include "ui/events/keycodes/keyboard_codes.h"
@@ skipping 38 matching lines @@
         !strcmp(classname, LabelButton::kViewClassName) ||
         !strcmp(classname, RadioButton::kViewClassName) ||
         !strcmp(classname, MenuButton::kViewClassName)) {
       return static_cast<CustomButton*>(view);
     }
   }
   return NULL;
 }
 
 CustomButton::~CustomButton() {
+  // InkDropDelegate needs to be destroyed by now since it may need to call
+  // methods on |this| via InkDropHost.
+  DCHECK(!ink_drop_delegate_);
 }
 
 void CustomButton::SetState(ButtonState state) {
   if (state == state_)
     return;
 
   if (animate_on_state_change_ &&
       (!is_throbbing_ || !hover_animation_->is_animating())) {
     is_throbbing_ = false;
     if ((state_ == STATE_HOVERED) && (state == STATE_NORMAL)) {
@@ skipping 341 matching lines @@
   return GetWidget() && GetWidget()->GetTopLevelWidget() != GetWidget();
 }
 
 bool CustomButton::FocusInChildWidget() const {
   return GetWidget() &&
          GetWidget()->GetRootView()->Contains(
              GetFocusManager()->GetFocusedView());
 }
 
 }  // namespace views