Add HttpProtocolHandler and convert everything to use it

net/url_request/http_protocol_handler.h

+// 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.
+
+#ifndef NET_URL_REQUEST_HTTP_PROTOCOL_HANDLER_H_
+#define NET_URL_REQUEST_HTTP_PROTOCOL_HANDLER_H_
+
+#include "net/url_request/url_request_job_factory.h"
+
+namespace net {
+
+class URLRequestJob;
+
+class NET_EXPORT HttpProtocolHandler
+    : public URLRequestJobFactory::ProtocolHandler {
+ public:
+  HttpProtocolHandler();
+  URLRequestJob* MaybeCreateJob(
+      URLRequest* request,
+      NetworkDelegate* network_delegate) const override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HttpProtocolHandler);
+};
+
+}  // namespace net
+
+#endif  // NET_URL_REQUEST_HTTP_PROTOCOL_HANDLER_H_