Remove enbale_xpc_notifications compile flag

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 499 matching lines @@
       if (target_cpu != "arm") {
         deps += [ "//gpu/tools/compositor_model_bench" ]
       }
     }
   }
 
   if (is_mac) {
     deps += [
       "//breakpad:crash_inspector",
       "//breakpad:dump_syms",
-
-      # XPC service is in developement and guarded against the
-      # enable_xpc_notifications, in the meantime however we still
-      # need compile coverage in the bots.
-      "//chrome/browser/ui/cocoa/notifications:alert_notification_xpc_service",
       "//third_party/apple_sample_code",
       "//third_party/molokocacao",
     ]
     deps -= [
       # Mojo in GN contains some things which are never compiled in GYP on Mac,
       # so compilation fails on Mac. They need porting.
       "//mojo",
     ]
   }
 
@@ skipping 559 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" ]
 }