UMA for Notification action buttons

third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp

Index: third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp
diff --git a/third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp b/third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp
index d916a0503ac76eaef6352b86f9d4853b8c0167e6..cdb3090b4873658552c5e3497a66ea4706a9a864 100644
--- a/third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp
+++ b/third_party/WebKit/Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp
@@ -60,6 +60,9 @@ ScriptPromise ServiceWorkerRegistrationNotifications::showNotification(ScriptSta
     if (exceptionState.hadException())
         return exceptionState.reject(scriptState);
 
+    // Log number of actions developer provided, even if it's more than we currently support.
+    Platform::current()->histogramCustomCounts("Notifications.PersistentNotificationActionCount", options.actions().size(), 0, 10, 12 /* one extra bucket for > 10 */);

[Alexei Svitkine (slow), 2015/10/28 19:09:09]

If you want a single bucket for each distinct counts (i.e. each bucket has a
range of 1 value), suggest using  histogramEnumeration(),

[johnme, 2015/10/29 14:24:41]

We don't strictly care about having distinct buckets, especially for larger
numbers of buttons (in practice it'd be useful for 0, 1 and 2 to have distinct
buckets). Converting the count to an enum feels rather hacky. So keeping it as a
histogram seems reasonable?

[Alexei Svitkine (slow), 2015/10/29 19:24:05]

Well, the way you're using counts() right now is equivalent to the enumeration
function. (Other than a few errors you have such as specifying a min 0 instead
of 1, since the API already gives you an underflow bucket from 0 to min value).
So it would be simpler and less error-prone to call that function.

On the other hand, if you don't mind having broader ranges at the high end, you
can actually specify a higher max value than 10 and continue using Counts().

I am ok with either approach, but your current one can be simplified using the
other function.

[johnme, 2015/11/23 15:06:09]

Gotcha. I've switched to histogramEnumeration/LinearHistogram as you suggested
since we care more about exact counts for small values than we care about the
order of magnitude for excessively large values provided (even though those are
possible, since this is developer-supplied input).

It feels a little dirty that we'll be deliberately making use of the underflow
bucket to pass in zeroes, but I guess that's normal?

+
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();