Record UMA statistics for file_stream operations.

net/base/file_stream_metrics_posix.cc

Index: net/base/file_stream_metrics_posix.cc
diff --git a/net/base/file_stream_metrics_posix.cc b/net/base/file_stream_metrics_posix.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b4eeb91d98e4ad65a09112dc4d5bcd352b16b872
--- /dev/null
+++ b/net/base/file_stream_metrics_posix.cc
@@ -0,0 +1,19 @@
+// 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/file_stream_metrics.h"
+
+namespace net {
+
+int ReduceErrorRange(int error) {
+  // No reduction necessary.
+  return error;
+}
+
+int MaxError() {
+  // Posix errors seem to have only low positive values.
+  return 160;
+}
+
+}  // namespace net