Adds a --deterministic-fetch flag to headless_shell

headless/public/util/deterministic_http_protocol_handler.cc

Index: headless/public/util/deterministic_http_protocol_handler.cc
diff --git a/headless/public/util/deterministic_http_protocol_handler.cc b/headless/public/util/deterministic_http_protocol_handler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ea98a44cd7eb31f480a23d11a2890d3c8dc461f8
--- /dev/null
+++ b/headless/public/util/deterministic_http_protocol_handler.cc
@@ -0,0 +1,67 @@
+// 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 "headless/public/util/deterministic_http_protocol_handler.h"
+
+#include "base/memory/ptr_util.h"
+#include "headless/public/headless_browser_context.h"
+#include "headless/public/util/deterministic_dispatcher.h"
+#include "headless/public/util/generic_url_request_job.h"
+#include "headless/public/util/http_url_fetcher.h"
+#include "net/url_request/url_request_context.h"
+
+namespace headless {
+
+class DeterministicHttpProtocolHandler::NopGenericURLRequestJobDelegate
+    : public GenericURLRequestJob::Delegate {
+ public:
+  NopGenericURLRequestJobDelegate() {}
+  ~NopGenericURLRequestJobDelegate() override {}
+
+  // GenericURLRequestJob::Delegate methods:
+  bool BlockOrRewriteRequest(
+      const GURL& url,
+      const std::string& referrer,
+      GenericURLRequestJob::RewriteCallback callback) override {
+    return false;
+  }
+
+  const GenericURLRequestJob::HttpResponse* MaybeMatchResource(
+      const GURL& url,
+      const net::HttpRequestHeaders& request_headers) override {
+    return nullptr;
+  }
+
+  void OnResourceLoadComplete(const GURL& final_url,
+                              const std::string& mime_type,
+                              int http_response_code) override {}
+};

[Sami, 2016/09/22 12:09:40]

DISALLOW_COPY_AND_ASSIGN

[alex clarke (OOO till 29th), 2016/09/23 13:29:21]

Done.

+
+DeterministicHttpProtocolHandler::DeterministicHttpProtocolHandler(
+    DeterministicDispatcher* deterministic_dispatcher)
+    : deterministic_dispatcher_(deterministic_dispatcher),
+      browser_context_(nullptr),
+      nop_delagate_(new NopGenericURLRequestJobDelegate()) {}
+
+DeterministicHttpProtocolHandler::~DeterministicHttpProtocolHandler() {}
+
+net::URLRequestJob* DeterministicHttpProtocolHandler::MaybeCreateJob(
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate) const {
+  std::unique_ptr<net::URLRequestContext> url_request_context(

[Sami, 2016/09/22 12:09:40]

This is a pretty big object. Could we construct it once and have all requests
share it like we do normally?

[alex clarke (OOO till 29th), 2016/09/23 13:29:21]

It's shared at the ProtocolHandler level now.

+      new net::URLRequestContext());
+
+  url_request_context->set_http_transaction_factory(

[Sami, 2016/09/22 12:09:40]

Should we use CopyFrom instead? Otherwise the context can miss a lot of subtle
things.

https://cs.chromium.org/chromium/src/net/url_request/url_request_context.h?l=...

[alex clarke (OOO till 29th), 2016/09/23 13:29:21]

Done.

+      browser_context_->GetRequestContext()->http_transaction_factory());
+
+  url_request_context->set_cookie_store(
+      browser_context_->GetRequestContext()->cookie_store());
+
+  return new GenericURLRequestJob(
+      request, network_delegate, deterministic_dispatcher_,
+      base::MakeUnique<HttpUrlFetcher>(std::move(url_request_context)),
+      nop_delagate_.get());
+}
+
+}  // namespace headless