Adds a new error for cases where a firewall may be the issue.

net/base/net_error_list.h

Index: net/base/net_error_list.h
===================================================================
--- net/base/net_error_list.h	(revision 63512)
+++ net/base/net_error_list.h	(working copy)
@@ -50,7 +50,7 @@
 // invalid assumption.
 NET_ERROR(UNEXPECTED, -9)
 
-// Permission to access a resource was denied.
+// Permission to access a resource, other than the network, was denied.
 NET_ERROR(ACCESS_DENIED, -10)
 
 // The operation failed because of unimplemented functionality.
@@ -66,7 +66,7 @@
 // from the expectation.
 NET_ERROR(UPLOAD_FILE_CHANGED, -14)
 
-// The socket is not connected
+// The socket is not connected.
 NET_ERROR(SOCKET_NOT_CONNECTED, -15)
 
 // A connection was closed (corresponding to a TCP FIN).
@@ -208,6 +208,11 @@
 // An error occurred when trying to do a name resolution (DNS).
 NET_ERROR(NAME_RESOLUTION_FAILED, -137)
 
+// Permission to access the network was denied. This is used to distinguish
+// access denied errors that were most likely caused by a firewall.
+// See also ERR_ACCESS_DENIED.
+NET_ERROR(NETWORK_ACCESS_DENIED, -138)
+
 // Certificate error codes
 //
 // The values of certificate error codes must be consecutive.