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

net/proxy/proxy_script_fetcher.h

 // 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.
 
 // ProxyScriptFetcher is an async interface for fetching a proxy auto config
 // script. It is specific to fetching a PAC script; enforces timeout, max-size,
 // status code.
 
 #ifndef NET_PROXY_PROXY_SCRIPT_FETCHER_H_
 #define NET_PROXY_PROXY_SCRIPT_FETCHER_H_
 #pragma once
 
 #include "base/string16.h"
 #include "net/base/completion_callback.h"
 
 class GURL;
 
 namespace net {
 
 class URLRequestContext;
 
 // Interface for downloading a PAC script. Implementations can enforce
 // timeouts, maximum size constraints, content encoding, etc..
 class ProxyScriptFetcher {
  public:
   // Destruction should cancel any outstanding requests.
   virtual ~ProxyScriptFetcher() {}
 
-  // Downloads the given PAC URL, and invokes |callback| on completion.
+  // Downloads a PAC script, and invokes |callback| on completion.
   // Returns OK on success, otherwise the error code. If the return code is
   // ERR_IO_PENDING, then the request completes asynchronously, and |callback|
   // will be invoked later with the final error code.
   // After synchronous or asynchronous completion with a result code of OK,
   // |*utf16_text| is filled with the response. On failure, the result text is
   // an empty string, and the result code is a network error. Some special
   // network errors that may occur are:
   //
   //    ERR_TIMED_OUT         -- the fetch took too long to complete.
   //    ERR_FILE_TOO_BIG      -- the response's body was too large.
   //    ERR_PAC_STATUS_NOT_OK -- non-200 HTTP status code.
   //    ERR_NOT_IMPLEMENTED   -- the response required authentication.
   //
   // If the request is cancelled (either using the "Cancel()" method or by
   // deleting |this|), then no callback is invoked.
   //
   // Only one fetch is allowed to be outstanding at a time.
-  virtual int Fetch(const GURL& url, string16* utf16_text,
+  virtual int Fetch(string16* utf16_text,
                     CompletionCallback* callback) = 0;
 
   // Aborts the in-progress fetch (if any).
   virtual void Cancel() = 0;
 
   // Returns the request context that this fetcher uses to issue downloads,
   // or NULL.
-  virtual URLRequestContext* GetRequestContext() = 0;
+  virtual URLRequestContext* GetRequestContext() const = 0;
+};
+
+// A proxy script fetcher that fetches a specific URL.
+class URLProxyScriptFetcher : public ProxyScriptFetcher {
+public:
+  // Sets the URL to retrieve when Fetch() is called.
+  virtual void SetURL(const GURL& url) = 0;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_SCRIPT_FETCHER_H_