Upstream the iOS web_shell and supporting code

ios/web/shell/shell_web_client.mm

+// 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 "ios/web/shell/shell_web_client.h"
+
+#include "ios/web/public/user_agent.h"
+#include "ios/web/shell/shell_web_main_parts.h"
+
+namespace web {
+
+ShellWebClient::ShellWebClient() {
+}
+
+ShellWebClient::~ShellWebClient() {
+}
+
+WebMainParts* ShellWebClient::CreateWebMainParts() {
+  web_main_parts_.reset(new ShellWebMainParts);
+  return web_main_parts_.get();
+}
+
+ShellBrowserState* ShellWebClient::browser_state() const {
+  return web_main_parts_->browser_state();
+}
+
+std::string ShellWebClient::GetProduct() const {
+  return "CriOS/36.77.34.45";
+}
+
+std::string ShellWebClient::GetUserAgent(bool desktop_user_agent) const {
+  std::string product = GetProduct();
+  return web::BuildUserAgentFromProduct(product);
+}
+
+}  // namespace web