Add a metric to Chrome to measure fragmentation of chrome.dll at startup.BUG=98033TEST=None

chrome/browser/fragmentation_checker_win.h

+// 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.
+
+#ifndef CHROME_BROWSER_FRAGMENTATION_CHECKER_WIN_H_
+#define CHROME_BROWSER_FRAGMENTATION_CHECKER_WIN_H_
+#pragma once
+
+#include "base/file_path.h"
+
+namespace fragmentation_checker {
+
+// Returns the count of the number of extents for the file at |file_path|. On

[grt (UTC plus 2), 2011/10/01 02:49:46]

Is "the count of the number of" different than "the number of"?

[robertshield, 2011/10/01 05:00:41]

Yes: http://www.youtube.com/watch?v=kQC82okzTXI

+// success, returns true and the count is placed in |file_extents_count|.
+bool CountFileExtents(const FilePath& file_path, uint32* file_extents_count);

[grt (UTC plus 2), 2011/10/01 02:49:46]

Style guide says not to use unsigned types just because something should never
be negative.  Did you chose uint32 because you need a full 32 bits?  Is int
appropriate?

[robertshield, 2011/10/01 05:00:41]

I chose it here because the ioctl returns a dword, so technically I could need
the full 32 bits, but that's silly since I cap the max number this function
returns, so changed to int.

+
+// Records fragmentation metrics for the current module. This records the number
+// of fragments the current module is stored in as well as the total on-disk

[grt (UTC plus 2), 2011/10/01 02:49:46]

remove " as well as the total on-disk..."

[robertshield, 2011/10/01 05:00:41]

Done.

+// span of those fragments.
+// This will be used to determine whether pursuing more aggressive
+// manual defragmentation is worth the effort.
+void RecordFragmentationMetricForCurrentModule();
+
+}  // namespace fragmentation_checker
+
+#endif  // CHROME_BROWSER_FRAGMENTATION_CHECKER_WIN_H_