Fixes a crash when InkDropDelegate gets destroyed after its InkDropHost

ui/views/controls/button/custom_button.cc

Index: ui/views/controls/button/custom_button.cc
diff --git a/ui/views/controls/button/custom_button.cc b/ui/views/controls/button/custom_button.cc
index bb4550098ee142bdc6194be9f87886aecb609036..6dd4d46521ab2f11e147fbd5ffe2a7dec4ec1d1c 100644
--- a/ui/views/controls/button/custom_button.cc
+++ b/ui/views/controls/button/custom_button.cc
@@ -56,6 +56,9 @@ CustomButton* CustomButton::AsCustomButton(views::View* view) {
 }
 
 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) {