AppListController refactoring part 1: AppListShower implementation.

ui/app_list/BUILD.gn

Index: ui/app_list/BUILD.gn
diff --git a/ui/app_list/BUILD.gn b/ui/app_list/BUILD.gn
index b90ba0e69b933abb9ec5cada8fb81c90caa18c16..6ff686e5cfcdd8abdd4d4059d1e44cbda599c49f 100644
--- a/ui/app_list/BUILD.gn
+++ b/ui/app_list/BUILD.gn
@@ -178,6 +178,16 @@ component("app_list") {
     ]
   }
 
+  if (use_ash) {
+    sources += [
+      "app_list_shower.h",
+      "app_list_shower_delegate.h",
+      "app_list_shower_delegate_factory.h",
+      "app_list_shower_impl.cc",
+      "app_list_shower_impl.h",
+    ]
+  }
+
   if (is_mac) {
     sources += [
       "cocoa/app_list_pager_view.h",
@@ -211,6 +221,8 @@ component("app_list") {
 
 static_library("test_support") {
   sources = [
+    "test/app_list_shower_impl_test_api.cc",
+    "test/app_list_shower_impl_test_api.h",
     "test/app_list_test_model.cc",
     "test/app_list_test_model.h",
     "test/app_list_test_view_delegate.cc",
@@ -329,6 +341,15 @@ test("app_list_unittests") {
     ]
   }
 
+  if (use_ash) {
+    sources += [ "app_list_shower_impl_unittest.cc" ]
+    deps += [
+      "//ui/aura:aura",
+      "//ui/aura:test_support",
+      "//ui/wm:wm",
+    ]
+  }
+
   if (is_mac) {
     sources += [
       "cocoa/app_list_view_controller_unittest.mm",