Implement chrome://network-error with network service.

content/browser/webui/network_error_url_loader.cc

+// Copyright 2017 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 "content/browser/webui/network_error_url_loader.h"
+
+#include "base/strings/string_number_conversions.h"
+#include "content/browser/webui/url_data_manager_backend.h"
+#include "content/public/common/url_constants.h"
+#include "net/base/net_errors.h"
+
+namespace content {
+
+void StartNetworkErrorsURLLoader(const ResourceRequest& request,
+                                 mojom::URLLoaderClientPtr client) {
+  int net_error = net::OK;

[scottmg, 2017/05/10 16:29:30]

Is this logic copied from somewhere else? It seems like defaulting to some sort
of error code (i.e not net::OK) would be a better default.

(I guess it's the code( in content/browser/webui/url_data_manager_backend.cc ?
It looks like an invalid error code would fallback URLRequestChromeJob in that
case.)

[jam, 2017/05/10 17:33:05]

Good point, defaulted to ERR_INVALID_URL which is the existing behavior.

+  if (request.url.host() == kChromeUIDinoHost) {
+    net_error = net::Error::ERR_INTERNET_DISCONNECTED;
+  } else {
+    std::string error_code_string = request.url.path().substr(1);
+
+    int temp_code;
+    if (base::StringToInt(error_code_string, &temp_code)) {
+      // Check for a valid error code.
+      if (URLDataManagerBackend::IsValidNetworkErrorCode(temp_code) &&
+          temp_code != net::Error::ERR_IO_PENDING) {
+        net_error = temp_code;
+      }
+    }
+  }
+
+  ResourceRequestCompletionStatus request_complete_data;
+  request_complete_data.error_code = net_error;
+  client->OnComplete(request_complete_data);
+}
+
+}  // namespace content