Remove implicit conversions from scoped_refptr to T* in android_webview/

android_webview/native/aw_contents_client_bridge.cc

 // Copyright (c) 2013 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 "android_webview/native/aw_contents_client_bridge.h"
 
 #include "android_webview/common/devtools_instrumentation.h"
 #include "android_webview/native/aw_contents.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
@@ skipping 361 matching lines @@
   }
   callback->Run(false, base::string16());
   pending_js_dialog_callbacks_.Remove(id);
 }
 
 // Use to cleanup if there is an error in client certificate response.
 void AwContentsClientBridge::HandleErrorInClientCertificateResponse(
     int request_id) {
   SelectCertificateCallback* callback =
       pending_client_cert_request_callbacks_.Lookup(request_id);
-  callback->Run(scoped_refptr<net::X509Certificate>());
+  callback->Run(nullptr);
   pending_client_cert_request_callbacks_.Remove(request_id);
 }
 
 bool RegisterAwContentsClientBridge(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android_webview