scoped_refptr: support opaque pointed-to classes via extern template

base/memory/ref_counted_unittest.cc

Index: base/memory/ref_counted_unittest.cc
diff --git a/base/memory/ref_counted_unittest.cc b/base/memory/ref_counted_unittest.cc
index e8eb0fd90f6c507912299eec14a53ef015e027c2..7e73bde1155db44e11eb2bdf071091782a648ce6 100644
--- a/base/memory/ref_counted_unittest.cc
+++ b/base/memory/ref_counted_unittest.cc
@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 #include "base/memory/ref_counted.h"
+
+#include "base/test/opaque_ref_counted.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
@@ -60,3 +62,13 @@ TEST(RefCountedUnitTest, ScopedRefPtrToSelf) {
   check->SelfDestruct();
   EXPECT_TRUE(ScopedRefPtrToSelf::was_destroyed());
 }
+
+TEST(RefCountedUnitTest, ScopedRefPtrToOpaque) {
+  scoped_refptr<base::OpaqueRefCounted> p = base::MakeOpaqueRefCounted();
+  base::TestOpaqueRefCounted(p);
+
+  scoped_refptr<base::OpaqueRefCounted> q;
+  q = p;
+  base::TestOpaqueRefCounted(p);
+  base::TestOpaqueRefCounted(q);
+}