Guard dbus component and config with assert(use_dbus)

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 383 matching lines @@
       "//rlz:rlz_lib",
       "//rlz:rlz_unittests",
     ]
   }
 
   if (is_linux) {
     # The following are definitely linux-only.
     deps += [
       "//chrome:manpage",
       "//chrome:xdg_mime",
-      "//dbus:dbus_test_server",
-      "//dbus:dbus_unittests",
       "//net:disk_cache_memory_test",
       "//net:flip_in_mem_edsm_server",
       "//net:flip_in_mem_edsm_server_unittests",
       "//net:quic_client",
       "//net:quic_server",
       "//sandbox/linux:chrome_sandbox",
       "//sandbox/linux:sandbox_linux_unittests",
     ]
 
+    if (use_dbus) {
+      deps += [
+        "//dbus:dbus_test_server",
+        "//dbus:dbus_unittests",
+      ]
+    }
+
     if (is_chromeos || use_ash) {
       deps += [ "//components/session_manager/core" ]
     }
 
     if (is_chrome_branded && is_official_build) {
       # TODO(dpranke): add the linux_dump_symbols flag?
       deps += [ "//chrome:linux_symbols" ]
     }
   }
 
@@ skipping 524 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" ]
 }