Don't preresolve DNS if a fixed proxy configuration is in place.

net/proxy/proxy_service.h

 // Copyright (c) 2012 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_PROXY_SERVICE_H_
 #define NET_PROXY_PROXY_SERVICE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 105 matching lines @@
   // the caller will not need to cancel the request.
   //
   // We use the three possible proxy access types in the following order,
   // doing fallback if one doesn't work.  See "pac_script_decider.h"
   // for the specifics.
   //   1.  WPAD auto-detection
   //   2.  PAC URL
   //   3.  named proxy
   //
   // Profiling information for the request is saved to |net_log| if non-NULL.
-  int ResolveProxy(const GURL& url,
-                   int load_flags,
-                   ProxyInfo* results,
-                   const net::CompletionCallback& callback,
-                   PacRequest** pac_request,
-                   NetworkDelegate* network_delegate,
-                   const BoundNetLog& net_log);
+  // This method is virtual for unit testing.
+  virtual int ResolveProxy(const GURL& url,
+                           int load_flags,
+                           ProxyInfo* results,
+                           const net::CompletionCallback& callback,
+                           PacRequest** pac_request,
+                           NetworkDelegate* network_delegate,
+                           const BoundNetLog& net_log);
 
   // This method is called after a failure to connect or resolve a host name.
   // It gives the proxy service an opportunity to reconsider the proxy to use.
   // The |results| parameter contains the results returned by an earlier call
   // to ResolveProxy.  The |net_error| parameter contains the network error
   // code associated with the failure. See "net/base/net_error_list.h" for a
   // list of possible values. The semantics of this call are otherwise
   // similar to ResolveProxy.
   //
   // NULL can be passed for |pac_request| if the caller will not need to
@@ skipping 27 matching lines @@
                              const BoundNetLog& net_log);
 
   // Called to report that the last proxy connection succeeded.  If |proxy_info|
   // has a non empty proxy_retry_info map, the proxies that have been tried (and
   // failed) for this request will be marked as bad. |network_delegate| will
   // be notified of any proxy fallbacks.
   void ReportSuccess(const ProxyInfo& proxy_info,
                      NetworkDelegate* network_delegate);
 
   // Call this method with a non-null |pac_request| to cancel the PAC request.
-  void CancelPacRequest(PacRequest* pac_request);
+  // This method is virtual for unit testing.
+  virtual void CancelPacRequest(PacRequest* pac_request);
 
   // Returns the LoadState for this |pac_request| which must be non-NULL.
   LoadState GetLoadState(const PacRequest* pac_request) const;
 
   // Sets the ProxyScriptFetcher and DhcpProxyScriptFetcher dependencies. This
   // is needed if the ProxyResolver is of type ProxyResolverWithoutFetch.
   // ProxyService takes ownership of both objects.
   void SetProxyScriptFetchers(
       ProxyScriptFetcher* proxy_script_fetcher,
       DhcpProxyScriptFetcher* dhcp_proxy_script_fetcher);
@@ skipping 238 matching lines @@
 
   // Whether child ProxyScriptDeciders should use QuickCheck
   bool quick_check_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyService);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_SERVICE_H_