Remove the implicit fallback to DIRECT when proxies fail. This better matches...

net/proxy/proxy_list.h

Index: net/proxy/proxy_list.h
===================================================================
--- net/proxy/proxy_list.h	(revision 35522)
+++ net/proxy/proxy_list.h	(working copy)
@@ -32,9 +32,13 @@
   // |scheme_bit_field| is a bunch of ProxyServer::Scheme bitwise ORed together.
   void RemoveProxiesWithoutScheme(int scheme_bit_field);
 
-  // Returns the first valid proxy server in the list.
-  ProxyServer Get() const;
+  // Returns true if there is nothing left in the ProxyList.
+  bool IsEmpty() const;
 
+  // Returns the first proxy server in the list. It is only valid to call
+  // this if !IsEmpty().
+  const ProxyServer& Get() const;
+
   // Set the list by parsing the pac result |pac_string|.
   // Some examples for |pac_string|:
   //   "DIRECT"