Draggable peeking/fullscreen launcher with transparent background.

ui/app_list/views/contents_view.h

Index: ui/app_list/views/contents_view.h
diff --git a/ui/app_list/views/contents_view.h b/ui/app_list/views/contents_view.h
index 435ff00450ed60e7b75bcf260597b53eab18d2a8..d5f3c406f9ea7f271b4d58ac92bd2fb47f04e3b6 100644
--- a/ui/app_list/views/contents_view.h
+++ b/ui/app_list/views/contents_view.h
@@ -27,6 +27,7 @@ namespace app_list {
 
 class AppsGridView;
 class AppListPage;
+class AppListView;
 class ApplicationDragAndDropHost;
 class AppListFolderItem;
 class AppListMainView;
@@ -46,7 +47,8 @@ class APP_LIST_EXPORT ContentsView : public views::View,
                                      public PaginationModelObserver,
                                      public AppListModelObserver {
  public:
-  explicit ContentsView(AppListMainView* app_list_main_view);
+  explicit ContentsView(AppListMainView* app_list_main_view,

[xiyuan, 2017/05/30 22:18:50]

nit: remove "explicit". It is only needed for single arg ctor (or there are args
with default value).

[newcomer, 2017/06/01 01:42:54]

Done.

+                        AppListView* app_list_view);
   ~ContentsView() override;
 
   // Initialize the pages of the launcher. Should be called after
@@ -200,6 +202,9 @@ class APP_LIST_EXPORT ContentsView : public views::View,
   // Parent view. Owned by the views hierarchy.
   AppListMainView* app_list_main_view_;
 
+  //  Owned by the views hierarchy.
+  AppListView* const app_list_view_;
+
   // Maps State onto |view_model_| indices.
   std::map<AppListModel::State, int> state_to_view_;