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 199b3e478a992b5a95d4b521681bff681b1bf5f9..ed29298866d58c5a9dfefc9751176b65cacbced8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -18854,9 +18854,20 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 <histogram name="GCM.DataMessageReceived" units="messages">
   <owner>peter@chromium.org</owner>
   <summary>
-    Number of DATA_MESSAGE messages for registered application IDs and
-    DELETED_MESSAGES messages for any registration ID received from Google Cloud
-    Messaging. Recorded when processing the received message.
+    Number of DATA_MESSAGE messages received from Google Cloud Messaging for
+    which a matching registration exists. Recorded when processing the received
+    message. Prior to M56 this also counted received DELETED_MESSAGES messages
+    (whether or not a registration existed).

[Ilya Sherman, 2016/12/08 06:54:56]

Typically I'd recommend renaming a histogram when its meaning changes.  I'd
encourage you to do so in this case as well, unless you have a strong reason not
to.

[johnme, 2016/12/12 20:43:33]

Yes, I've renamed things in the past. But in this case the DELETED_MESSAGES case
is believed to be such a tiny fraction of the DATA_MESSAGE volume, that this
shouldn't cause any meaningful jump in the graph. Or to put it another way, the
effective meaning of the metric isn't changing, this should just make its
interpretation simpler.

+  </summary>
+</histogram>
+
+<histogram name="GCM.DataMessageReceivedHasCollapseKey"
+    enum="BooleanHasCollapseKey">
+  <owner>peter@chromium.org</owner>
+  <summary>
+    Records whether a non-empty collapse_key token is set for each received
+    DATA_MESSAGE message from Google Cloud Messaging for which a matching
+    registration exists. Recorded while processing the received message.
   </summary>
 </histogram>
 
@@ -18864,9 +18875,20 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
     enum="BooleanRegistered">
   <owner>peter@chromium.org</owner>
   <summary>
-    Records whether a corresponding registration was found for each received
-    DATA_MESSAGE or DELETED_MESSAGES message from Google Cloud Messaging.
-    Recorded while processing the received message.
+    Records whether a matching registration was found for each received
+    DATA_MESSAGE message from Google Cloud Messaging. Recorded while processing
+    the received message. Prior to M56 this also counted received
+    DELETED_MESSAGES messages.
+  </summary>
+</histogram>
+
+<histogram name="GCM.DeletedMessagesReceived" units="messages">
+  <owner>peter@chromium.org</owner>
+  <summary>
+    For every DELETED_MESSAGES message received from Google Cloud Messaging
+    (whether or not a matching registration exists), this records the provided
+    count of how many messages were simultaneously deleted, or zero if the count
+    is unknown.
   </summary>
 </histogram>
 
@@ -77029,6 +77051,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Hardware accelerated"/>
 </enum>
 
+<enum name="BooleanHasCollapseKey" type="int">
+  <int value="0" label="No collapse_key"/>
+  <int value="1" label="Has collapse_key"/>
+</enum>
+
 <enum name="BooleanHasCrc" type="int">
   <int value="0" label="No CRC"/>
   <int value="1" label="Has CRC"/>