Guard dbus component and config with assert(use_dbus)

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/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
 
 gypi_values = exec_script("//build/gypi_to_gn.py",
@@ skipping 489 matching lines @@
     deps += [
       "//ui/base/ime",
       "//ui/events:dom_keycode_converter",
     ]
   }
   if (is_linux) {  # Both desktop Linux and ChromeOS.
     sources += rebase_path(gypi_values.chrome_browser_ui_linux_sources,
                            ".",
                            "//chrome")
     if (use_aura) {
-      deps += [
-        "//build/linux:fontconfig",
-        "//dbus",
-      ]
+      deps += [ "//build/linux:fontconfig" ]
+      if (use_dbus) {
+        deps += [ "//dbus" ]
+      }
     }
     if (use_x11) {
       sources += rebase_path(gypi_values.chrome_browser_ui_x11_sources,
                              ".",
                              "//chrome")
       configs += [ "//build/config/linux:x11" ]
       deps += [ "//ui/events/devices" ]
       if (is_chromeos) {
         sources -= [ "views/tabs/window_finder_x11.cc" ]
       }
@@ skipping 169 matching lines @@
     "//chrome/browser",
     "//content/public/browser",
     "//content/public/common",
     "//content/test:test_support",
     "//net:test_support",
     "//skia",
     "//testing/gtest",
     "//ui/base",
   ]
 }