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 2f8df067687647edf40dbeec32e4f83d2dddac51..25fa01e9dee8d2d3b55c3f6054a656f15ebbd845 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13589,6 +13589,37 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Number of calls to extension functions.</summary>
 </histogram>
 
+<histogram name="Extensions.Functions.FailedTotalExecutionTime" units="ms">
+  <owner>rdevlin.cronin@chromium.org</owner>
+  <summary>
+    The total amount of time it took to execute an extension function that
+    succeeded from the time the extension function is called to the time the

[Mark P, 2016/05/03 18:30:39]

succeed -> failed

[Devlin, 2016/05/03 20:43:01]

Done.

+    function responds. Note that since some extension functions are inherently

[Mark P, 2016/05/03 18:30:39]

Is it possible to fail without responding (e.g., a timeout)?

[Devlin, 2016/05/03 20:43:01]

Theoretically, we should always respond.  If we don't, it's a bug (and maybe
these and following metrics could help track it down).

+    slow (anything that requires user interaction, for instance), this is not a
+    definitive source for function performance.
+  </summary>
+</histogram>
+
+<histogram name="Extensions.Functions.SucceededTotalExecutionTime" units="ms">
+  <owner>rdevlin.cronin@chromium.org</owner>
+  <summary>
+    The total amount of time it took to execute an extension function that
+    succeeded from the time the extension function is called to the time the
+    function responds. Note that since some extension functions are inherently
+    slow (anything that requires user interaction, for instance), this is not a
+    definitive source for function performance.
+  </summary>
+</histogram>
+
+<histogram name="Extensions.Functions.SynchronousExecutionTime" units="ms">

[Mark P, 2016/05/03 18:30:39]

I see this is recorded in two places in the code.  Are you sure you want both
places a function can be executed to be summed into the same histogram?  (Are
they conceptually the same?)

[Devlin, 2016/05/03 20:43:01]

Yep, they are conceptually the same.

+  <owner>rdevlin.cronin@chromium.org</owner>
+  <summary>
+    The synchronous amount of time an extension function takes. Note that many
+    extension functions run asynchronously; see also
+    Extensions.Functions.[Succeeded|Failed]TotalExecutionTime.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.GetUserDataTempDir" enum="GetUserDataTempDirResult">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>