do not require xscrnsaver on CrOS

build/linux/system.gyp

 # 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.
 
 {
   'variables': {
     'conditions': [
       ['sysroot!=""', {
         'pkg-config': '<(chroot_cmd) ./pkg-config-wrapper "<(sysroot)" "<(target_arch)"',
         # libgcrypt-config-wrapper invokes libgcrypt-config directly from the 
@@ skipping 288 matching lines @@
           'link_settings': {
             'ldflags': [
               '<!@(<(pkg-config) --libs-only-L --libs-only-other xrender)',
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l xrender)',
             ],
           },
         },
         {
-          'target_name': 'xscrnsaver',
-          'type': 'none',
-          'direct_dependent_settings': {
-            'cflags': [
-              '<!@(<(pkg-config) --cflags xscrnsaver)',
-            ],
-          },
-          'link_settings': {
-            'ldflags': [
-              '<!@(<(pkg-config) --libs-only-L --libs-only-other xscrnsaver)',
-            ],
-            'libraries': [
-              '<!@(<(pkg-config) --libs-only-l xscrnsaver)',
-            ],
-          },
-        },
-        {
           'target_name': 'xtst',
           'type': 'none',
           'toolsets': ['host', 'target'],
           'conditions': [
             ['_toolset=="target"', {
               'direct_dependent_settings': {
                 'cflags': [
                   '<!@(<(pkg-config) --cflags xtst)',
                 ],
               },
@@ skipping 17 matching lines @@
                 ],
                 'libraries': [
                   '<!@(pkg-config --libs-only-l xtst)',
                 ],
               },
             }]
           ]
         }
       ],  # targets
     }],
+    ['use_x11==1 and chromeos==0', {
+      'targets': [
+        {
+          'target_name': 'xscrnsaver',
+          'type': 'none',
+          'direct_dependent_settings': {
+            'cflags': [
+              '<!@(<(pkg-config) --cflags xscrnsaver)',
+            ],
+          },
+          'link_settings': {
+            'ldflags': [
+              '<!@(<(pkg-config) --libs-only-L --libs-only-other xscrnsaver)',
+            ],
+            'libraries': [
+              '<!@(<(pkg-config) --libs-only-l xscrnsaver)',
+            ],
+          },
+        },
+      ],  # targets
+    }],
     ['use_evdev_gestures==1', {
       'targets': [
         {
           'target_name': 'libevdev-cros',
           'type': 'none',
           'direct_dependent_settings': {
             'cflags': [
               '<!@(<(pkg-config) --cflags libevdev-cros)'
             ],
           },
@@ skipping 671 matching lines @@
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l libudev)',
             ],
           },
         }],
       ],
     },
   ],
 }