[iOS/OS X] Allow base::scoped_nsobject<> to be used when ARC is enabled.

base/mac/scoped_nsobject_unittest.mm

Index: base/mac/scoped_nsobject_unittest.mm
diff --git a/base/mac/scoped_nsobject_unittest.mm b/base/mac/scoped_nsobject_unittest.mm
index 8b0b97df3a72df06e987cd09032bd23cbd2a05f2..cefb5fe19fbb29ac1f0a91667497b13f353a3fe4 100644
--- a/base/mac/scoped_nsobject_unittest.mm
+++ b/base/mac/scoped_nsobject_unittest.mm
@@ -8,8 +8,16 @@
 #include "base/mac/scoped_nsobject.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+// See scoped_nsobject_unittest_arc.mm for why this is necessary. Remove once
+// gyp support is dropped.
+void ScopedNSObjectUnittestArcLinkerWorkaround();
+
 namespace {
 
+TEST(ScopedNSObjectTest, EnableARCTests) {
+  ScopedNSObjectUnittestArcLinkerWorkaround();
+}
+
 TEST(ScopedNSObjectTest, ScopedNSObject) {
   base::scoped_nsobject<NSObject> p1([[NSObject alloc] init]);
   ASSERT_TRUE(p1.get());