Upstream the iOS web_shell and supporting code

ios/web/shell/shell_web_client.h

+// 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.
+
+#ifndef IOS_WEB_SHELL_SHELL_WEB_CLIENT_H_
+#define IOS_WEB_SHELL_SHELL_WEB_CLIENT_H_
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "ios/web/public/web_client.h"
+
+namespace web {
+class ShellBrowserState;
+class ShellWebMainParts;
+
+class ShellWebClient : public WebClient {
+ public:
+  ShellWebClient();
+  ~ShellWebClient() override;
+
+  // WebClient implementation.
+  WebMainParts* CreateWebMainParts() override;
+  std::string GetProduct() const override;
+  std::string GetUserAgent(bool desktop_user_agent) const override;
+
+  ShellBrowserState* browser_state() const;
+
+ private:
+  scoped_ptr<ShellWebMainParts> web_main_parts_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShellWebClient);
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_SHELL_SHELL_WEB_CLIENT_H_