Deliver errors from devtools API calls to callbacks

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/bind.h"
 #include "base/json/json_reader.h"
@@ skipping 108 matching lines @@
     return false;
   auto it = pending_messages_.find(id);
   if (it == pending_messages_.end()) {
     NOTREACHED() << "Unexpected reply";
     return false;
   }
   Callback callback = std::move(it->second);
   pending_messages_.erase(it);
   if (!callback.callback_with_result.is_null()) {
     const base::DictionaryValue* result_dict;
-    if (!message_dict.GetDictionary("result", &result_dict)) {
-      NOTREACHED() << "Badly formed reply result";
+    if (message_dict.GetDictionary("result", &result_dict)) {
+      callback.callback_with_result.Run(*result_dict);
+    } else if (message_dict.GetDictionary("error", &result_dict)) {
+      std::unique_ptr<base::Value> null_value = base::Value::CreateNullValue();
+      DLOG(ERROR) << "Error in method call result: " << *result_dict;
+      callback.callback_with_result.Run(*null_value);
+    } else {
+      NOTREACHED() << "Reply has neither result nor error";
       return false;
     }
-    callback.callback_with_result.Run(*result_dict);
   } else if (!callback.callback.is_null()) {
     callback.callback.Run();
   }
   return true;
 }
 
 bool HeadlessDevToolsClientImpl::DispatchEvent(
     std::unique_ptr<base::Value> owning_message,
     const base::DictionaryValue& message_dict) {
   std::string method;
@@ skipping 235 matching lines @@
 HeadlessDevToolsClientImpl::Callback::Callback(
     base::Callback<void(const base::Value&)> callback)
     : callback_with_result(callback) {}
 
 HeadlessDevToolsClientImpl::Callback::~Callback() {}
 
 HeadlessDevToolsClientImpl::Callback& HeadlessDevToolsClientImpl::Callback::
 operator=(Callback&& other) = default;
 
 }  // namespace headless