Draggable peeking/fullscreen launcher with transparent background.

ui/app_list/views/app_list_main_view.cc

 // Copyright 2013 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/app_list/views/app_list_main_view.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 36 matching lines @@
     : delegate_(delegate),
       model_(delegate->GetModel()),
       search_box_view_(nullptr),
       contents_view_(nullptr) {
   SetLayoutManager(
       features::IsAnswerCardEnabled()
           ? static_cast<views::LayoutManager*>(new views::FillLayout)
           : static_cast<views::LayoutManager*>(
                 new views::BoxLayout(views::BoxLayout::kVertical, 0, 0, 0)));
   model_->AddObserver(this);
+  SetPaintToLayer();

[xiyuan, 2017/05/24 18:28:18]

Remove this. Or remove the call in AppListView::InitContents.

[newcomer, 2017/05/25 23:10:51]

Done.

 }
 
 AppListMainView::~AppListMainView() {
   model_->RemoveObserver(this);
 }
 
 void AppListMainView::Init(gfx::NativeView parent,
                            int initial_apps_page,
                            SearchBoxView* search_box_view) {
   search_box_view_ = search_box_view;
@@ skipping 146 matching lines @@
     contents_view_->search_results_page_view()->SetSelection(select);
 }
 
 void AppListMainView::OnResultInstalled(SearchResult* result) {
   // Clears the search to show the apps grid. The last installed app
   // should be highlighted and made visible already.
   search_box_view_->ClearSearch();
 }
 
 }  // namespace app_list