Report histogram creation results.

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 b5facb3a68dc1b75d673410404dacf7b63c29e12..991dedd0309f2e9579a1d15a0d2421626a6daabd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -52982,6 +52982,45 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="UMA.Histograms.browser.Creations"

[Alexei Svitkine (slow), 2016/03/01 16:41:34]

I suggest using the <histogram_suffixes> construct to make the XML more concise.
See top of the file for an example.

[bcwhite, 2016/03/02 19:14:20]

Okay.  It doesn't seem to provide an option for omitting the source histogram
but that works out well here because I can remove the "browser" one which will
also remove the setting of that name (if empty) in startup.

+    enum="HistogramCreationReport">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Type and flags of every histogram created. Counts are not mutually-exclusive
+    except for the different types.
+  </summary>
+</histogram>
+
+<histogram name="UMA.Histograms.gpu-process.Creations"
+    enum="HistogramCreationReport">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Type and flags of every histogram created. Counts are not mutually-exclusive
+    except for the different types.
+  </summary>
+</histogram>
+
+<histogram name="UMA.Histograms.renderer.Creations"
+    enum="HistogramCreationReport">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Type and flags of every histogram created. Counts are not mutually-exclusive
+    except for the different types.
+  </summary>
+</histogram>
+
+<histogram name="UMA.Histograms.setup.Creations" enum="HistogramCreationReport">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Type and flags of every histogram created. Counts are not mutually-exclusive
+    except for the different types.
+  </summary>
+</histogram>
+
 <histogram name="UMA.InitSequence" enum="UmaInitSequence">
   <owner>asvitkine@chromium.org</owner>
   <summary>
@@ -69155,6 +69194,20 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Both devices, pointing and keyboard, detected."/>
 </enum>
 
+<enum name="HistogramCreationReport" type="int">
+  <int value="0" label="Total number of reports created"/>
+  <int value="1" label="Total number of histograms created"/>
+  <int value="2" label="Total number of histograms existing"/>
+  <int value="3" label="Number of general histograms"/>

[Alexei Svitkine (slow), 2016/03/01 16:41:34]

Nit: I think "general histogram" is not very obvious - I would call say "Log
histogram"

[bcwhite, 2016/03/02 19:14:20]

Done.

+  <int value="4" label="Number of linear histograms"/>
+  <int value="5" label="Number of boolean histograms"/>
+  <int value="6" label="Number of custom histograms"/>
+  <int value="7" label="Number of sparse histograms"/>
+  <int value="8" label="Number of UMA-targeted histograms"/>
+  <int value="9" label="Number of UMA-stability histograms"/>
+  <int value="10" label="Number of persistent histograms"/>

[Alexei Svitkine (slow), 2016/03/01 16:41:34]

Nit: No need to put "Total number" and "number" in these labels. Just describe
the event - i.e. "Linear histogram created".

[bcwhite, 2016/03/02 19:14:20]

Done.

+</enum>
+
 <enum name="HistoryFaviconsRecoveryEnum" type="int">
   <summary>Error states noted in thumbnail_database.cc recovery code.</summary>
   <int value="0" label="RECOVERY_EVENT_RECOVERED">Successful recovery.</int>