Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_error_observer.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.
 
 #ifndef NET_PROXY_PROXY_RESOLVER_ERROR_OBSERVER_H_
 #define NET_PROXY_PROXY_RESOLVER_ERROR_OBSERVER_H_
 
 #include "base/basictypes.h"
 #include "base/string16.h"
 #include "net/base/net_export.h"
 
 namespace net {
 
-// Interface for observing JavaScript error messages from PAC scripts. The
-// default implementation of the ProxyResolverJSBindings takes a class
-// implementing this interface and forwards all JavaScript errors related to
-// PAC scripts.
+// Interface for observing JavaScript error messages from PAC scripts.

[mmenke, 2013/01/29 20:19:08]

May want to mention that this can be called on any thread.

[eroman, 2013/01/29 22:51:23]

Done.

It is ambiguous what thread this will be called on, since this interface isn't
tied to any particular implementation (for instance if used from the
multithreaded proxy resolver it could be any of the workers).

I have added a generic comment.

 class NET_EXPORT_PRIVATE ProxyResolverErrorObserver {
  public:
   ProxyResolverErrorObserver() {}
   virtual ~ProxyResolverErrorObserver() {}
 
   // Handler for when an error is encountered. |line_number| may be -1
   // if a line number is not applicable to this error. |error| is a message
   // describing the error.
   virtual void OnPACScriptError(int line_number, const string16& error) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverErrorObserver);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_ERROR_OBSERVER_H_