Implement support for fallback update check urls in the component updater

components/component_updater/request_sender.cc

Index: components/component_updater/request_sender.cc
diff --git a/components/component_updater/request_sender.cc b/components/component_updater/request_sender.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8c80622ad7d0f07b2c51e4fadcac65ae51f3e57f
--- /dev/null
+++ b/components/component_updater/request_sender.cc
@@ -0,0 +1,65 @@
+// Copyright 2014 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 "components/component_updater/request_sender.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/sequenced_task_runner.h"
+#include "components/component_updater/component_updater_configurator.h"
+#include "components/component_updater/component_updater_utils.h"
+#include "net/url_request/url_fetcher.h"
+
+namespace component_updater {
+
+RequestSender::RequestSender(const Configurator& config) : config_(config) {
+}
+
+RequestSender::~RequestSender() {
+}
+
+void RequestSender::Send(const std::string& request_string,
+                         const std::vector<GURL>& urls,
+                         const RequestSenderCallback& request_sender_callback) {
+  if (urls.empty()) {
+    request_sender_callback.Run(NULL);
+    return;
+  }
+
+  request_string_ = request_string;
+  urls_ = urls;
+  request_sender_callback_ = request_sender_callback;
+
+  cur_url_ = urls_.begin();
+
+  SendInternal();
+}
+
+void RequestSender::SendInternal() {
+  DCHECK(cur_url_ != urls_.end());
+  DCHECK(cur_url_->is_valid());
+
+  url_fetcher_.reset(SendProtocolRequest(
+      *cur_url_, request_string_, this, config_.RequestContext()));
+}
+
+void RequestSender::OnURLFetchComplete(const net::URLFetcher* source) {
+  if (GetFetchError(*source) == 0) {
+    request_sender_callback_.Run(source);
+    return;
+  }
+
+  if (++cur_url_ != urls_.end() &&
+      config_.GetSequencedTaskRunner()->PostTask(
+          FROM_HERE,
+          base::Bind(&RequestSender::SendInternal, base::Unretained(this)))) {
+    return;
+  }
+
+  request_sender_callback_.Run(source);
+}
+
+}  // namespace component_updater