Enable chrome://gcm-internals on Android

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 b4d637fa8986b8c5ea82c7c4958fd14df0a2ec7a..5cb17a7bb9f02734ccfe56ab22710f106ba0c2ca 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -14371,6 +14371,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GCM.DataMessageReceived" units="messages">

[Alexei Svitkine (slow), 2015/12/17 18:20:52]

Looks like this is logged via:
 UMA_HISTOGRAM_COUNTS("GCM.DataMessageReceived", 1);

That's inefficient, since it allocated 50 buckets to ever use one of them. It
would be better to use UMA_HISTOGRAM_BOOLEAN().

However, given that these histograms were never in the xml suggests that maybe
no one ever used them. In that case, perhaps it's better to simply remove them?

[Peter Beverloo, 2015/12/18 17:19:17]

Ah, got it! Changed.
At least for Android, there's value in them because I'd like to know how many
messages we receive as Chrome, and how many of those we can deliver using the
Push API. I suspect that we have a bug here (unsubscription behaviour is odd),
but this is hard to validate locally.

[Alexei Svitkine (slow), 2015/12/18 19:18:42]

Okay. My other issue with these histogram is they only log a value of "1" and
never anything else. This usually makes histograms have limited value, because
without other info it doesn't tell you much. e.g. what does a value like 33443
tell you? It would depend on other factors, like how many people are on that
channel/platform, how many people are using this feature, etc.

Usually, it's better to also log false in addition to true, which tells you at
least what percentage of messages (are received?).

From your description, it also sounds like you want something similar ("messages
we receive as Chrome, and how many of those we can deliver using the Push API")
- i.e. it sounds this should be one enum histogram with two buckets - one for
message receivedand one for message delivered.

+  <owner>jianli@chromium.org</owner>
+  <owner>peter@chromium.org</owner>
+  <summary>Total number of GCM data messages received.</summary>
+</histogram>
+
 <histogram name="GCM.FirstReceivedDataMessageLatencyAfterConnection"
     units="milliseconds">
   <owner>juyik@chromium.org</owner>
@@ -14452,6 +14458,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GCM.RegistrationRequest" units="requests">
+  <owner>jianli@chromium.org</owner>
+  <owner>peter@chromium.org</owner>
+  <summary>Total number of GCM registration requests.</summary>

[jianli, 2015/12/18 00:10:00]

Mark this Android only if this is only intended for Android. Otherwise, please
also add it to the desktop version.

[Peter Beverloo, 2015/12/18 17:19:17]

The desktop version already records these.

+</histogram>
+
 <histogram name="GCM.RegistrationRequestStatus"
     enum="GCMRegistrationRequestStatus">
   <owner>juyik@chromium.org</owner>
@@ -14534,6 +14546,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GCM.UnregistrationRequest" units="requests">
+  <owner>jianli@chromium.org</owner>
+  <owner>peter@chromium.org</owner>
+  <summary>Total number of GCM unregistration requests.</summary>
+</histogram>
+
 <histogram name="GCM.UnregistrationRequestStatus"
     enum="GCMUnregistrationRequestStatus">
   <owner>juyik@chromium.org</owner>