Pushed InkDropHost inheritence up to CustomButton.

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 313 matching lines @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // CustomButton, gfx::AnimationDelegate implementation:
 
 void CustomButton::AnimationProgressed(const gfx::Animation* animation) {
   SchedulePaint();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// CustomButton, views::InkDropHost implementation:
+
+void CustomButton::AddInkDropLayer(ui::Layer* ink_drop_layer) {
+  SetPaintToLayer(true);
+  SetFillsBoundsOpaquely(false);

[sadrul, 2016/01/06 19:18:45]

It shouldn't happen here. At most, this should DCHECK() that layer() exists.
Even then, I don't think it's entirely right.

Is there a reason a ButtonInkDropHost wouldn't work?

+  layer()->Add(ink_drop_layer);
+  layer()->StackAtBottom(ink_drop_layer);
+}
+
+void CustomButton::RemoveInkDropLayer(ui::Layer* ink_drop_layer) {
+  layer()->Remove(ink_drop_layer);
+  SetFillsBoundsOpaquely(true);
+  SetPaintToLayer(false);
+}
+
+gfx::Point CustomButton::CalculateInkDropCenter() const {
+  return GetLocalBounds().CenterPoint();
+}
+
+////////////////////////////////////////////////////////////////////////////////
 // CustomButton, protected:
 
 CustomButton::CustomButton(ButtonListener* listener)
     : Button(listener),
       state_(STATE_NORMAL),
       hover_animation_(this),
       animate_on_state_change_(true),
       is_throbbing_(false),
       triggerable_event_flags_(ui::EF_LEFT_MOUSE_BUTTON),
       request_focus_on_press_(true),
@@ skipping 78 matching lines @@
   return GetWidget() && GetWidget()->GetTopLevelWidget() != GetWidget();
 }
 
 bool CustomButton::FocusInChildWidget() const {
   return GetWidget() &&
          GetWidget()->GetRootView()->Contains(
              GetFocusManager()->GetFocusedView());
 }
 
 }  // namespace views