headless: Fix handling of replies without any parameters

headless/lib/browser/headless_devtools_client_impl.cc

 // Copyright 2016 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 "headless/lib/browser/headless_devtools_client_impl.h"
 
 #include <memory>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
@@ skipping 77 matching lines @@
     NOTREACHED() << "Badly formed reply";
     return;
   }
   int id = 0;
   DCHECK(message_dict->GetInteger("id", &id));
   auto it = pending_messages_.find(id);
   if (it == pending_messages_.end()) {
     NOTREACHED() << "Unexpected reply";
     return;
   }
-  base::DictionaryValue* result_dict;
-  if (message_dict->GetDictionary("result", &result_dict)) {
+  if (!it->second.callback_with_result.is_null()) {
+    base::DictionaryValue* result_dict;
+    if (!message_dict->GetDictionary("result", &result_dict)) {
+      NOTREACHED() << "Badly formed reply result";
+      return;
+    }
     it->second.callback_with_result.Run(*result_dict);
-  } else {
+  } else if (!it->second.callback.is_null()) {
     it->second.callback.Run();
   }
   pending_messages_.erase(it);
 }
 
 void HeadlessDevToolsClientImpl::AgentHostClosed(
     content::DevToolsAgentHost* agent_host,
     bool replaced_with_another_client) {
   DCHECK_EQ(agent_host_, agent_host);
   agent_host = nullptr;
@@ skipping 187 matching lines @@
     base::Callback<void(const base::Value&)> callback)
     : callback_with_result(callback) {}
 
 HeadlessDevToolsClientImpl::PendingMessage::~PendingMessage() {}
 
 HeadlessDevToolsClientImpl::PendingMessage&
 HeadlessDevToolsClientImpl::PendingMessage::operator=(PendingMessage&& other) =
     default;
 
 }  // namespace headless