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_);

[sadrul, 2015/12/07 18:04:17]

It seems somewhat unfortunate to require the subclass to have to explicitly
destroy this, when CustomButton is the owner. Would it be possible to reset
state from, e.g. View::ViewHierarchyChanged() callback when the View is
unparented instead ('reset state' is not necessarily destroy, though, since the
button could be moved from one view to another, and in that case, just any
in-progress animation should be canceled, without affecting ink-drop effects
from future interaction)?

[varkha, 2015/12/07 21:35:29]

Done.

 }
 
 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