mac: Don't use -Werror on third-party code in official builds.

BUG=none
TEST=official builders go green

Review URL: https://chromiumcodereview.appspot.com/10382068

git-svn-id: http://src.chromium.org/svn/trunk/src/build@135896 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -1550,6 +1550,13 @@
             'xcode_settings': {
               'WARNING_CFLAGS!': ['-Wall', '-Wextra'],
             },
+            'conditions': [
+              ['buildtype=="Official"', {
+                'xcode_settings': {
+                  'GCC_TREAT_WARNINGS_AS_ERRORS': 'NO',    # -Werror
+                },
+              }],
+            ],
           }],
         ],
       }, {