Convert JsonWriter::Write to taking a const ref for the in-param

sync/test/accounts_client/test_accounts_client_unittest.cc

Index: sync/test/accounts_client/test_accounts_client_unittest.cc
diff --git a/sync/test/accounts_client/test_accounts_client_unittest.cc b/sync/test/accounts_client/test_accounts_client_unittest.cc
index f73a43bcefd7e5306e4ae8722cf75eda18a3d311..b60c533ad210b06dc55646ff7538f19d5552299a 100644
--- a/sync/test/accounts_client/test_accounts_client_unittest.cc
+++ b/sync/test/accounts_client/test_accounts_client_unittest.cc
@@ -67,7 +67,7 @@ TEST(TestAccountsClientTest, ClaimAccountSuccess) {
   success_dict.Set("expiration_time", new base::StringValue(kExpirationTime));
 
   string success_response;
-  base::JSONWriter::Write(&success_dict, &success_response);
+  base::JSONWriter::Write(success_dict, &success_response);
   EXPECT_CALL(client, SendRequest(_, _))
       .WillOnce(DoAll(SetArgPointee<1>(success_response), Return(true)));