Revert 241681 "Let test_isolation_mode default to check on mac."

trunk/src/build/common.gypi

Index: trunk/src/build/common.gypi
===================================================================
--- trunk/src/build/common.gypi	(revision 241704)
+++ trunk/src/build/common.gypi	(working copy)
@@ -780,10 +780,12 @@
         # overriden with GYP_DEFINES.
         # TODO(maruel): Remove the conditions as more configurations are
         # supported.
+        # TODO(csharp): Remove OS!="mac" once xcode can run the isolate code
+        # again.
         # NOTE: The check for disable_nacl==0 and component=="static_library"
         # can't be used here because these variables are not defined yet, but it
         # is still not supported.
-        ['OS!="ios" and OS!="android" and chromeos==0', {
+        ['OS!="mac" and OS!="ios" and OS!="android" and chromeos==0', {
           'test_isolation_mode%': 'check',
         }, {
           'test_isolation_mode%': 'noop',