Do not define OS_CHROMEOS for untrusted NaCl code

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 0c1d4152a92ca5ee6835890d98df0baf7a3b4bc3..bdd0c9ba1f282654e8a142feb36160c7c2df2236 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2447,9 +2447,6 @@
       ['enable_one_click_signin==1', {
         'defines': ['ENABLE_ONE_CLICK_SIGNIN'],
       }],
-      ['chromeos==1', {
-        'defines': ['OS_CHROMEOS=1'],
-      }],
       ['use_xi2_mt!=0 and use_x11==1', {
         'defines': ['USE_XI2_MT=<(use_xi2_mt)'],
       }],
@@ -2785,6 +2782,9 @@
       ['<(use_nss)==1 and >(nacl_untrusted_build)==0', {
         'defines': ['USE_NSS=1'],
       }],
+      ['<(chromeos)==1 and >(nacl_untrusted_build)==0', {
+        'defines': ['OS_CHROMEOS=1'],
+      }],
       ['enable_wexit_time_destructors==1', {
         'conditions': [
           [ 'clang==1', {