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

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 5276585ba9c6410cf0752e0653ed4348a24c8203..0859d2b89ed7171c60cb3fcbe52cf72068d6542f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -406,6 +406,48 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="WinTimeTicks.ChangedCores" enum="WindowsVersion">
+  <summary>
+    Incremented each time the TimeTicks field trial completes and switched cores
+    at least once. Broken down by Windows version.
+  </summary>
+</histogram>
+
+<histogram name="WinTimeTicks.MinResolutionNanoseconds" units="microseconds">

[jar (doing other things), 2013/04/12 02:14:54]

nit: units should be nanoseconds

[James Simonsen, 2013/04/12 02:29:46]

Doh. Fixed.

+  <summary>
+    The smallest non-zero delta reported by subsequent calls to
+    QueryPerformanceCounter.
+  </summary>
+</histogram>
+
+<histogram name="WinTimeTicks.NonDecreasing" enum="WindowsVersion">
+  <summary>
+    The number of times the TimeTicks field trial reported non-decreasing
+    QueryPerformanceCounter values. Broken down by Windows version.
+  </summary>
+</histogram>
+
+<histogram name="WinTimeTicks.NonStopTsc">
+  <summary>
+    True if the CPU's time stamp counter ticks at a constant rate regardless of
+    CPU frequency.
+  </summary>
+</histogram>
+
+<histogram name="WinTimeTicks.VersionSuccessful" enum="WindowsVersion">
+  <summary>
+    The number of times the TimeTicks field trial succeeded. Broken down by
+    Windows version.
+  </summary>
+</histogram>
+
+<histogram name="WinTimeTicks.VersionTotal" enum="WindowsVersion">
+  <summary>
+    The number of times the TimeTicks field trial ran for comparison with
+    WinTimeTicks.VersionSuccess. Broken down by Windows version.
+  </summary>
+</histogram>
+
 </histograms>
 
 <!-- Enum types -->
@@ -1357,6 +1399,15 @@ other types of suffix sets.
   <int value="11" label="Require phone number"/>
 </enum>
 
+<enum name="WindowsVersion" type="int">
+  <int value="0" label="Pre-XP"/>
+  <int value="1" label="XP"/>
+  <int value="2" label="2003 Server"/>
+  <int value="3" label="Vista"/>
+  <int value="4" label="7"/>

[jar (doing other things), 2013/04/12 02:14:54]

nit: probably "Windows 7" would be better (so it doesn't look like you didn't
put in a label... and it is displaying a number).

Same thing for "8"

[James Simonsen, 2013/04/12 02:29:46]

Done.

+  <int value="5" label="8"/>
+</enum>
+
 </enums>
 
 <!-- Field trials -->