Avoid to change layer type in InkDropHostView::AddInkDropLayer

ui/views/animation/ink_drop_host_view.cc

 // Copyright 2016 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/animation/ink_drop_host_view.h"
 
 #include "base/memory/ptr_util.h"
 #include "ui/events/event.h"
 #include "ui/events/scoped_target_handler.h"
 #include "ui/gfx/color_palette.h"
@@ skipping 108 matching lines @@
       old_paint_to_layer_(false),
       destroying_(false) {}
 
 InkDropHostView::~InkDropHostView() {
   // TODO(bruthig): Improve InkDropImpl to be safer about calling back to
   // potentially destroyed InkDropHosts and remove |destroying_|.
   destroying_ = true;
 }
 
 void InkDropHostView::AddInkDropLayer(ui::Layer* ink_drop_layer) {
+  DCHECK(!layer() || layer()->type() == ui::LAYER_TEXTURED);

[sky, 2017/02/22 21:29:49]

Please add a comment as to why this expects ui::LAYER_TEXTURED. Do you know that
this may happen? If so, when?

[yiyix, 2017/02/22 23:15:39]

I tried to answer your questions in the description of this cl. Is it more clear
now?

   old_paint_to_layer_ = layer() != nullptr;
   SetPaintToLayer();
   layer()->SetFillsBoundsOpaquely(false);
   ink_drop_mask_ = CreateInkDropMask();
   if (ink_drop_mask_)
     ink_drop_layer->SetMaskLayer(ink_drop_mask_->layer());
   layer()->Add(ink_drop_layer);
   layer()->StackAtBottom(ink_drop_layer);
 }
 
@@ skipping 149 matching lines @@
 std::unique_ptr<InkDropImpl>
 InkDropHostView::CreateDefaultFloodFillInkDropImpl() {
   std::unique_ptr<views::InkDropImpl> ink_drop =
       InkDropHostView::CreateDefaultInkDropImpl();
   ink_drop->SetAutoHighlightMode(
       views::InkDropImpl::AutoHighlightMode::SHOW_ON_RIPPLE);
   return ink_drop;
 }
 
 }  // namespace views