Move enable_app_list to a buildflag.

chrome/browser/ui/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/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 444 matching lines @@
     # dependencies block below, rather than here.
     "//base",
     "//chrome:extra_resources",
     "//chrome:resources",
     "//chrome:strings",
     "//chrome/app:chrome_dll_resources",
     "//chrome/app:command_ids",
     "//chrome/app/resources:platform_locale_settings",
     "//chrome/app/theme:chrome_unscaled_resources",
     "//chrome/app/theme:theme_resources",
+    "//chrome/browser:resource_prefetch_predictor_proto",
     "//chrome/browser/devtools",
     "//chrome/browser/ui/webui/engagement:mojo_bindings",
     "//chrome/browser/ui/webui/omnibox:mojo_bindings",
     "//chrome/browser/ui/webui/plugins:mojo_bindings",
     "//chrome/browser/ui/webui/usb_internals:mojo_bindings",
     "//chrome/common",
     "//chrome/common/net",
     "//chrome/installer/util:with_no_strings",
     "//components/app_modal",
     "//components/autofill/content/browser:risk_proto",
@@ skipping 2941 matching lines @@
       "test/test_confirm_bubble_model.cc",
       "test/test_confirm_bubble_model.h",
     ]
     deps += [ "//chrome/test:test_support_ui" ]
   }
 
   if (enable_extensions) {
     deps += [ "//extensions/browser" ]
   }
 }