Create FieldTrialAllocator.Size histogram

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 b3c39a9c8012bc97f5fc19e2ba08ae9a5a5e5a46..e3ed73833593de800301a3f541b38e3f4bcf08d5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -66238,6 +66238,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="UMA.Metrics.FieldTrialAllocator.Size" units="bytes">

[Alexei Svitkine (slow), 2016/10/26 20:53:20]

UNA.Metrics. is redundant - just UMA. is fine.

[lawrencewu, 2016/10/26 21:04:22]

Done.

+  <owner>lawrencewu@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <owner>asvitkine@chromium.org</owner>
+  <summary>
+    Size, before padding, of objects allocated from persistent memory in the
+    browser process for field trials. Updated on each subprocess launch.
+  </summary>
+</histogram>
+
 <histogram name="UMA.MetricsIDsReset" enum="BooleanHit">
   <owner>jwd@chromium.org</owner>
   <summary>
@@ -66289,27 +66299,6 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="UMA.PersistentAllocator.FieldTrialAllocator.Allocs"
-    units="bytes">

[Alexei Svitkine (slow), 2016/10/26 20:53:20]

You added these in an earlier CL - and you're removing them because we never end
up logging them? Is that the case?

[lawrencewu, 2016/10/26 21:04:22]

Yes, that is the case.

-  <owner>lawrencewu@chromium.org</owner>
-  <owner>bcwhite@chromium.org</owner>
-  <owner>asvitkine@chromium.org</owner>
-  <summary>
-    Size, before padding, of objects allocated from persistent memory in the
-    browser process for field trials. This is updated with every allocation.
-  </summary>
-</histogram>
-
-<histogram name="UMA.PersistentAllocator.FieldTrialAllocator.UsedPct" units="%">
-  <owner>lawrencewu@chromium.org</owner>
-  <owner>bcwhite@chromium.org</owner>
-  <owner>asvitkine@chromium.org</owner>
-  <summary>
-    Percentage of persistent memory segment that has been allocated. This is
-    updated only once per reporting cycle.
-  </summary>
-</histogram>
-
 <histogram name="UMA.PersistentAllocator.GpuMetrics.Allocs" units="bytes">
   <owner>bcwhite@chromium.org</owner>
   <owner>asvitkine@chromium.org</owner>