Add HttpProtocolHandler and convert everything to use it

net/url_request/http_protocol_handler.cc

+// 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.
+
+#include "net/url_request/http_protocol_handler.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
+#include "net/url_request/url_request_error_job.h"
+#include "net/url_request/url_request_http_job.h"
+#include "net/url_request/url_request_redirect_job.h"
+#include "url/gurl.h"
+
+namespace net {
+
+HttpProtocolHandler::HttpProtocolHandler() {}
+
+URLRequestJob* HttpProtocolHandler::MaybeCreateJob(
+    URLRequest* request,
+    NetworkDelegate* network_delegate) const {
+  return URLRequestHttpJob::Factory(request, network_delegate,

[mmenke, 2016/04/21 20:58:01]

I think we should get rid of URLRequestHttpJob::Factory, and make this take its
place.  I'm not sure how much extra work that would be - may make sense to do
that in another CL.

[mgersh, 2016/04/22 20:27:15]

The reason why I didn't end up doing that is because the URLRequestHttpJob
constructor is protected, which I figured was so people don't try to use it and
accidentally bypass HSTS, and there are a few calls to
URLRequestHttpJob::Factory in various unit tests which I couldn't easily replace
with uses of a protocol handler and it seemed ugly to add them as friend
classes. So I'm not sure what a good way to do it would be.

[mmenke, 2016/04/22 20:41:04]

I'd say it's best just to make URLRequestHttpJob's constructor.  We could make
this a public inner class of URLRequestHttpJob, but I don't think it's worth the
extra layer of obfuscation.

[mgersh, 2016/04/27 16:13:52]

Done (assuming you meant make it public), and added a comment.

+                                    request->url().scheme());
+}
+
+}  // namespace net