Adds support for the DHCP portion of the WPAD (proxy auto-discovery) protocol.

net/proxy/dhcp_proxy_script_fetcher_factory.h

Index: net/proxy/dhcp_proxy_script_fetcher_factory.h
diff --git a/net/proxy/dhcp_proxy_script_fetcher_factory.h b/net/proxy/dhcp_proxy_script_fetcher_factory.h
new file mode 100644
index 0000000000000000000000000000000000000000..20e4104d8ee88e22ebb3131edb0093cfa53ed2f0
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+++ b/net/proxy/dhcp_proxy_script_fetcher_factory.h
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+// Copyright (c) 2011 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_PROXY_DHCP_SCRIPT_FETCHER_FACTORY_H_
+#define NET_PROXY_DHCP_SCRIPT_FETCHER_FACTORY_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/memory/singleton.h"
+#include "net/base/completion_callback.h"
+#include "net/url_request/url_request_context.h"
+
+namespace net {
+
+class DhcpProxyScriptFetcher;
+
+// Factory object for creating the appropriate concrete base class of
+// DhcpProxyScriptFetcher for your operating system and settings.
+//
+// You might think we could just implement a DHCP client at the protocol
+// level and have cross-platform support for retrieving PAC configuration
+// from DHCP, but unfortunately the DHCP protocol assumes there is a single
+// client per machine (specifically per network interface card), and there
+// is an implicit state machine between the client and server, so adding a
+// second client to the machine would not be advisable (see e.g. some
+// discussion of what can happen at this URL:
+// http://www.net.princeton.edu/multi-dhcp-one-interface-handling.html).
+//
+// Therefore, we have platform-specific implementations, and so we use
+// this factory to select the right one.
+class DhcpProxyScriptFetcherFactory {
+ public:
+  // Creates a new factory object with default settings.
+  DhcpProxyScriptFetcherFactory();
+
+  // Ownership is transferred to the caller. url_request_context must be valid
+  // and its lifetime must exceed that of the returned DhcpProxyScriptFetcher.
+  //
+  // Note that while a request is in progress, the fetcher may be holding a
+  // reference to |url_request_context|. Be careful not to create cycles
+  // between the fetcher and the context; you can break such cycles by calling
+  // Cancel().
+  DhcpProxyScriptFetcher* Create(URLRequestContext* url_request_context);
+
+  // Attempts to enable/disable the DHCP WPAD feature.  Does nothing
+  // if |IsSupported()| returns false.
+  //
+  // The current default is |enabled() == false|.
+  void set_enabled(bool enabled);
+
+  // Returns true if the DHCP WPAD feature is enabled.  Always returns
+  // false if |IsSupported()| is false.
+  bool enabled() const;
+
+  // Returns true if the DHCP WPAD feature is supported on the current
+  // operating system.
+  static bool IsSupported();
+
+ protected:
+  bool feature_enabled_;
+
+  DISALLOW_COPY_AND_ASSIGN(DhcpProxyScriptFetcherFactory);
+};
+
+}  // namespace net
+
+#endif  // NET_PROXY_DHCP_SCRIPT_FETCHER_FACTORY_H_