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 112 matching lines @@
   //
   // 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);
 
+  // Returns true if the proxy information could be determined without spawning
+  // an asynchronous task.  Otherwise, |result| is unmodified.
+  bool TryResolveProxySynchronously(const GURL& raw_url,
+                                    int load_flags,
+                                    ProxyInfo* result,
+                                    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
   // cancel the request.
@@ skipping 171 matching lines @@
   void OnInitProxyResolverComplete(int result);
 
   // Returns ERR_IO_PENDING if the request cannot be completed synchronously.
   // Otherwise it fills |result| with the proxy information for |url|.
   // Completing synchronously means we don't need to query ProxyResolver.
   int TryToCompleteSynchronously(const GURL& url,
                                  int load_flags,
                                  NetworkDelegate* network_delegate,
                                  ProxyInfo* result);
 
+  // Identical to ResolveProxy, except that |callback| is permitted to be null.
+  // if |callback.is_null()|, this function becomes a thin wrapper around
+  // |TryToCompleteSynchronously|.
+  int ResolveProxyHelper(const GURL& url,
+                         int load_flags,
+                         ProxyInfo* results,
+                         const net::CompletionCallback& callback,
+                         PacRequest** pac_request,
+                         NetworkDelegate* network_delegate,
+                         const BoundNetLog& net_log);
+
   // Cancels all of the requests sent to the ProxyResolver. These will be
   // restarted when calling SetReady().
   void SuspendAllPendingRequests();
 
   // Advances the current state to |STATE_READY|, and resumes any pending
   // requests which had been stalled waiting for initialization to complete.
   void SetReady();
 
   // Returns true if |pending_requests_| contains |req|.
   bool ContainsPendingRequest(PacRequest* req);
@@ skipping 94 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_