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

base/mac/scoped_nsobject_unittest.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <vector>
 
 #include "base/mac/scoped_nsautorelease_pool.h"
 #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());
   ASSERT_EQ(1u, [p1 retainCount]);
   base::scoped_nsobject<NSObject> p2(p1);
   ASSERT_EQ(p1.get(), p2.get());
   ASSERT_EQ(2u, [p1 retainCount]);
   p2.reset();
   ASSERT_EQ(nil, p2.get());
   ASSERT_EQ(1u, [p1 retainCount]);
@@ skipping 61 matching lines @@
   base::scoped_nsobject<id> p2([[NSObject alloc] init]);
   ASSERT_TRUE(o1 != p2);
   ASSERT_FALSE(o1 == p2);
   id o2 = p2.get();
   swap(p1, p2);
   ASSERT_EQ(o2, p1.get());
   ASSERT_EQ(o1, p2.get());
 }
 
 }  // namespace