[iOS/ARC] Fix a violation of ODR in base::BindBlock under ARC.

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 457962d94189b40bb4345aa66dfc82580ed6c789..72d524225829573f7bd50b81476d0be394293174 100644
--- a/base/mac/scoped_nsobject_unittest.mm
+++ b/base/mac/scoped_nsobject_unittest.mm
@@ -8,16 +8,8 @@
 #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());