Experimental app list: "All apps" button has a folder-like icon.

ui/app_list/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/ui.gni")
 
 component("app_list") {
   sources = [
     "app_list_constants.cc",
     "app_list_constants.h",
     "app_list_export.h",
     "app_list_folder_item.cc",
     "app_list_folder_item.h",
     "app_list_item.cc",
     "app_list_item.h",
     "app_list_item_observer.h",
     "app_list_item_list.cc",
     "app_list_item_list.h",
     "app_list_item_list_observer.h",
     "app_list_menu.cc",
     "app_list_menu.h",
     "app_list_model.cc",
     "app_list_model.h",
     "app_list_model_observer.h",
     "app_list_switches.cc",
     "app_list_switches.h",
     "app_list_view_delegate.cc",
     "app_list_view_delegate.h",
+    "folder_image.cc",
+    "folder_image.h",
     "folder_image_source.cc",
     "folder_image_source.h",
     "pagination_controller.cc",
     "pagination_controller.h",
     "pagination_model.cc",
     "pagination_model.h",
     "pagination_model_observer.h",
     "search_box_model.cc",
     "search_box_model.h",
     "search_box_model_observer.h",
@@ skipping 171 matching lines @@
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/resources",
   ]
 }
 
 test("app_list_unittests") {
   sources = [
     "app_list_item_list_unittest.cc",
     "app_list_model_unittest.cc",
+    "folder_image_unittest.cc",
     "pagination_model_unittest.cc",
     "search/history_data_store_unittest.cc",
     "search/mixer_unittest.cc",
     "search/term_break_iterator_unittest.cc",
     "search/tokenized_string_char_iterator_unittest.cc",
     "search/tokenized_string_match_unittest.cc",
     "search/tokenized_string_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
@@ skipping 35 matching lines @@
       "cocoa/app_list_view_controller_unittest.mm",
       "cocoa/app_list_window_controller_unittest.mm",
       "cocoa/apps_grid_controller_unittest.mm",
       "cocoa/apps_search_box_controller_unittest.mm",
       "cocoa/apps_search_results_controller_unittest.mm",
       "cocoa/test/apps_grid_controller_test_helper.h",
       "cocoa/test/apps_grid_controller_test_helper.mm",
     ]
   }
 }