Don't depend on (empty) chromeos-only display target

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index 0b0f11a63b9d7dde72d2f6f27db27db9945b9289..aa8ab77ec991e6f10edf90f1a915be48ae61cc5a 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -1205,7 +1205,6 @@
         '../skia/skia.gyp:skia',
         '../testing/gtest.gyp:gtest',
         '../ui/accessibility/accessibility.gyp:ax_gen',
-        '../ui/display/display.gyp:display',
         'ash_shell_lib',
         'ash_test_support',
       ],
@@ -1213,6 +1212,13 @@
         'shell/window_watcher_unittest.cc',
         'test/ash_unittests.cc',
       ],
+      'conditions': [
+        ['chromeos==1', {
+          'dependencies': [
+            '../ui/display/display.gyp:display',
+          ],
+        }],
+      ],
     },
   ],
 }