Use AuthCredentials throughout the network stack instead of username/password.

net/base/zap.cc

+// 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.
+
+#include "net/base/zap.h"
+
+namespace net {
+
+void ZapBuf(void* buf, size_t buf_len) {
+  memset(buf, 0x0, buf_len);
+}
+
+void ZapString(std::string* s) {
+  if (!s->empty())
+    ZapBuf(&(*s)[0], s->length() * sizeof(char));
+}
+
+void ZapString(string16* s) {
+  if (!s->empty())
+    ZapBuf(&(*s)[0], s->length() * sizeof(char16));
+}
+
+}  // net