AppListController refactoring part 1: AppListShower implementation.

BUILD.gn

 # Copyright (c) 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 222 matching lines @@
   }
 
   if (toolkit_views) {
     deps += [ "//ui/views:views_unittests" ]
   }
 
   if (use_aura) {
     deps += [
       "//ash:ash_shell_with_content",
       "//ash:ash_unittests",
+      "//ui/app_list/shower:app_list_shower_unittests",
       "//ui/aura:aura_unittests",
       "//ui/aura:demo",
       "//ui/wm:wm_unittests",
     ]
   }
 
   if (use_ozone) {
     deps += [ "//ui/ozone" ]
   }
 
@@ skipping 649 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }