Add PendingEvents UMA to ConnectionEventTracker shutdown.

google_apis/gcm/engine/connection_event_tracker.cc

Index: google_apis/gcm/engine/connection_event_tracker.cc
diff --git a/google_apis/gcm/engine/connection_event_tracker.cc b/google_apis/gcm/engine/connection_event_tracker.cc
index d8c3313135f23abc256bb807c1b535449a61d483..b76921599a29bc18d1f6ecb1de2e8bc6ed7c8e9f 100644
--- a/google_apis/gcm/engine/connection_event_tracker.cc
+++ b/google_apis/gcm/engine/connection_event_tracker.cc
@@ -4,6 +4,7 @@
 
 #include "google_apis/gcm/engine/connection_event_tracker.h"
 
+#include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "net/base/network_change_notifier.h"
 
@@ -19,7 +20,10 @@ namespace gcm {
 
 ConnectionEventTracker::ConnectionEventTracker() = default;
 
-ConnectionEventTracker::~ConnectionEventTracker() = default;
+ConnectionEventTracker::~ConnectionEventTracker() {
+  UMA_HISTOGRAM_ENUMERATION("GCM.PendingEvents", completed_events_.size(),

[Peter Beverloo, 2016/12/22 11:24:36]

Let's call this PendingConnectionEventsAtShutdown?

[harkness, 2016/12/23 13:52:56]

Done.

+                            kMaxClientEvents + 1);
+}
 
 void ConnectionEventTracker::StartConnectionAttempt() {
   // TODO(harkness): Can we dcheck here that there is not an in progress