x11: Make sure USE_XI2_MT is defined only for use_x11=1.

build/common.gypi

 # Copyright (c) 2012 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 1998 matching lines @@
         # TODO(erg): We are progressively sealing up use of deprecated features
         # in gtk in preparation for an eventual porting to gtk3.
         'defines': ['GTK_DISABLE_SINGLE_INCLUDES=1'],
       }],
       ['chromeos==1', {
         'defines': ['OS_CHROMEOS=1'],
       }],
       ['google_tv==1', {
         'defines': ['GOOGLE_TV=1'],
       }],
-      ['use_xi2_mt!=0', {
+      ['use_xi2_mt!=0 and use_x11==1', {
         'defines': ['USE_XI2_MT=<(use_xi2_mt)'],
       }],
       ['file_manager_extension==1', {
         'defines': ['FILE_MANAGER_EXTENSION=1'],
       }],
       ['image_loader_extension==1', {
         'defines': ['IMAGE_LOADER_EXTENSION=1'],
       }],
       ['profiling==1', {
         'defines': ['ENABLE_PROFILING=1'],
@@ skipping 2715 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }