Make DBUS an optional dependency so Chromium can be built without it....

build/common.gypi

 # Copyright (c) 2010 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 463 matching lines @@
         'libjpeg_gyp_path': '../third_party/libjpeg/libjpeg.gyp',
       }],  # use_libjpeg_turbo==1
 
       # Use GConf, the GNOME configuration system.
       ['chromeos==1', {
         'use_gconf%': 0,
       }, {
         'use_gconf%': 1,
       }],
 
+      # Use DBUS on Linux.
+      ['OS=="linux"', {
+        'use_dbus%': 1,
+      }, {
+        'use_dbus%': 0,
+      }],
+
       # Setup -D flags passed into grit.
       ['chromeos==1', {
         'grit_defines': ['-D', 'chromeos'],
       }],
       ['toolkit_views==1', {
         'grit_defines': ['-D', 'toolkit_views'],
       }],
       ['touchui==1', {
         'grit_defines': ['-D', 'touchui'],
       }],
@@ skipping 1124 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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