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

base/mac/bind_objc_block_unittest.mm

Index: base/mac/bind_objc_block_unittest.mm
diff --git a/base/mac/bind_objc_block_unittest.mm b/base/mac/bind_objc_block_unittest.mm
index c0e690c00832be63638f2505cec385a778bb06df..f3c189cd4b7dd4108c5b80f8e12fde49446ee768 100644
--- a/base/mac/bind_objc_block_unittest.mm
+++ b/base/mac/bind_objc_block_unittest.mm
@@ -11,8 +11,16 @@
 #include "base/callback_helpers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+// See bind_objc_block_unittest_arc.mm for why this is necessary. Remove once
+// gyp support is dropped.
+void BindObjcBlockUnittestArcLinkerWorkaround();
+
 namespace {
 
+TEST(BindObjcBlockTest, EnableARCTests) {
+  BindObjcBlockUnittestArcLinkerWorkaround();
+}
+
 TEST(BindObjcBlockTest, TestScopedClosureRunnerExitScope) {
   int run_count = 0;
   int* ptr = &run_count;