Adds a --deterministic-fetch flag to headless_shell

headless/public/util/http_url_fetcher.h

Index: headless/public/util/http_url_fetcher.h
diff --git a/headless/public/util/http_url_fetcher.h b/headless/public/util/http_url_fetcher.h
new file mode 100644
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+++ b/headless/public/util/http_url_fetcher.h
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+// 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 HEADLESS_PUBLIC_UTIL_HTTP_URL_FETCHER_H_
+#define HEADLESS_PUBLIC_UTIL_HTTP_URL_FETCHER_H_
+
+#include "base/macros.h"
+#include "headless/public/util/url_fetcher.h"
+
+namespace net {
+class URLRequestContext;
+class URLRequestJobFactory;
+}  // namespace
+
+namespace headless {
+
+// This URLFetcher owns a (mostly) empty URLRequestContext which it uses to
+// fetch, bypassing any user-specified protocol handlers.
+class HttpUrlFetcher : public URLFetcher {
+ public:
+  explicit HttpUrlFetcher(
+      std::unique_ptr<net::URLRequestContext> url_request_context);
+  ~HttpUrlFetcher() override;
+
+  // URLFetcher implementation:
+  void StartFetch(const GURL& rewritten_url,
+                  const net::HttpRequestHeaders& request_headers,
+                  ResultListener* result_listener) override;
+
+ private:
+  class Delegate;
+
+  std::unique_ptr<net::URLRequestContext> url_request_context_;
+  std::unique_ptr<net::URLRequestJobFactory> url_request_job_factory_;
+  std::unique_ptr<Delegate> delagate_;
+
+  DISALLOW_COPY_AND_ASSIGN(HttpUrlFetcher);
+};
+
+}  // namespace headless
+
+#endif  // HEADLESS_PUBLIC_UTIL_HTTP_URL_FETCHER_H_