Update a WARNING with a bug URL.

net/proxy/proxy_service.cc

Index: net/proxy/proxy_service.cc
diff --git a/net/proxy/proxy_service.cc b/net/proxy/proxy_service.cc
index daf0913ba14f6c20f7352dae0d60a6f2c70e9a45..438f147d7a752a3d8ec2c693854ecbd8af2fe94d 100644
--- a/net/proxy/proxy_service.cc
+++ b/net/proxy/proxy_service.cc
@@ -354,11 +354,11 @@ ProxyService* ProxyService::Create(const ProxyInfo* pi) {
   return new ProxyService(new ProxyConfigServiceMac(),
                           new ProxyResolverMac());
 #else
-  // This used to be a NOTIMPLEMENTED(), but that logs as an error,
-  // screwing up layout tests.
-  LOG(WARNING) << "Proxies are not implemented; remove me once that's fixed.";
-  // http://code.google.com/p/chromium/issues/detail?id=4523 is the bug
-  // to implement this.
+  // TODO(port): implement ProxyConfigServiceLinux as well as make use of
+  // ProxyResolverV8 once it's implemented.
+  // See:
+  // - http://code.google.com/p/chromium/issues/detail?id=8143
+  // - http://code.google.com/p/chromium/issues/detail?id=2764
   return CreateNull();
 #endif
 }