Create a field trial to test if we can detect good QPC implementations.

chrome/browser/metrics/time_ticks_experiment_win.h

Index: chrome/browser/metrics/time_ticks_experiment_win.h
diff --git a/chrome/browser/metrics/time_ticks_experiment_win.h b/chrome/browser/metrics/time_ticks_experiment_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..65f60aae8036082f9ed0e169e5569d18f0a7b93c
--- /dev/null
+++ b/chrome/browser/metrics/time_ticks_experiment_win.h
@@ -0,0 +1,24 @@
+// Copyright (c) 2013 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_METRICS_TIME_TICKS_EXPERIMENT_WIN_H_
+#define CHROME_BROWSER_METRICS_TIME_TICKS_EXPERIMENT_WIN_H_
+
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+
+namespace chrome_browser_metrics {

[darin (slow to review), 2013/04/22 18:25:05]

I'm not a fan of this style of namespace.  I think we should either use no
namespace or just a chrome:: namespace corresponding to the top-level directory.

There was some discussion about this back in 2010:
https://groups.google.com/a/chromium.org/forum/?fromgroups=#!topic/chromium-d...

More recently, I've grown increasingly convinced that the approach taken by
src/content and src/net is best.  That is, just have a namespace corresponding
to the top-level directory, and then prefix your classes for name-grouping below
that.  Avoid nested namespaces.

It looks like just the tracking_synchronization* files make use of this
namespace currently.

+
+// Runs an experiment once per session upon successful upload of UMA. Determines
+// if QueryPerformanceCounter() is safe to use generally on this system. Ensures
+// that the resolution is better than 1ms, returns quickly, and is monotonically
+// increasing. Records the results in UMA for the next upload.
+void CollectTimeTicksStats();
+
+}  // namespace chrome_browser_metrics
+
+#endif  // defined(OS_WIN)
+
+#endif  // CHROME_BROWSER_METRICS_TIME_TICKS_EXPERIMENT_WIN_H_