Record UMA statistics for file_stream operations.

net/base/file_stream_metrics.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/file_stream_metrics.h"
+
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+
+namespace net {
+
+namespace {
+
+void RecordFileErrorTypeCount(FileErrorSource source) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "FileErrorType.Counts", source, FILE_ERROR_SOURCE_COUNT);
+}
+
+}  // namespace
+
+void RecordFileError(int error, FileErrorSource source, bool record) {
+  if (!record)
+    return;
+
+  RecordFileErrorTypeCount(source);
+
+  int bucket = GetErrorBucket(error);

[cbentzel, 2011/08/23 01:52:02]

Rather than write logic to figure out which bucket to use, you could use

UMA_HISTOGRAM_CUSTOM_ENUMERATION

and then per-platform you will only need something to come up with the bucket
ranges. 

[cbentzel, 2011/08/30 14:48:23]

As we discussed, I'm OK with the approach you took instead of using
UMA_HISTOGRAM_CUSTOM_ENUMERATION.

+
+  static const int max_bucket = MaxBucket();  // Fixed value per platform.
+  static const int max_error = MaxError();  // Fixed value per platform.
+
+  switch(source) {
+    case FILE_ERROR_SOURCE_OPEN:
+      UMA_HISTOGRAM_ENUMERATION("FileError.Open", error, max_error);

[cbentzel, 2011/08/23 01:52:02]

This should be 

Net.FileOpen_Error
Net.FileOpen_ErrorRange

or similar, so this is cleaner in the dashboard.

[ahendrickson, 2011/08/31 19:39:52]

Done.

+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.Open", bucket, max_bucket);
+      break;
+

[cbentzel, 2011/08/23 01:52:02]

Nit: most code I've seen doesn't have newlines between the break; and the next
case, but I think it makes this clearer. It doesn't appear to be against the
style guide either.

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Vertical_White...

+    case FILE_ERROR_SOURCE_WRITE:
+      UMA_HISTOGRAM_ENUMERATION("FileError.Write", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.Write", bucket, max_bucket);
+      break;
+
+    case FILE_ERROR_SOURCE_READ:
+      UMA_HISTOGRAM_ENUMERATION("FileError.Read", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.Read", bucket, max_bucket);
+      break;
+
+    case FILE_ERROR_SOURCE_SEEK:
+      UMA_HISTOGRAM_ENUMERATION("FileError.Seek", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.Seek", bucket, max_bucket);
+      break;
+
+    case FILE_ERROR_SOURCE_FLUSH:
+      UMA_HISTOGRAM_ENUMERATION("FileError.Flush", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.Flush", bucket, max_bucket);
+      break;
+
+    case FILE_ERROR_SOURCE_SET_EOF:
+      UMA_HISTOGRAM_ENUMERATION("FileError.SetEof", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.SetEof", bucket, max_bucket);
+      break;
+
+    case FILE_ERROR_SOURCE_GET_SIZE:
+      UMA_HISTOGRAM_ENUMERATION("FileError.GetSize", error, max_error);
+      UMA_HISTOGRAM_ENUMERATION("FileErrorRange.GetSize", bucket, max_bucket);
+      break;
+
+    default:
+      break;
+  }
+}
+
+}  // namespace net