Update ConnectionEventTracker to check if there is an in progress attempt.

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 cad77ebd37e1387c8c24e1fadc0d7ca85401beaa..223cafcf0e38c84fbe8c7dc028a33ebaeb2c13bd 100644
--- a/google_apis/gcm/engine/connection_event_tracker.cc
+++ b/google_apis/gcm/engine/connection_event_tracker.cc
@@ -32,17 +32,22 @@ void ConnectionEventTracker::StartConnectionAttempt() {
 }
 
 void ConnectionEventTracker::EndConnectionAttempt() {
-  // TODO(harkness): Modify tests so that we can put a DCHECK here.

[Peter Beverloo, 2017/01/11 14:31:48]

Why isn't the TODO relevant anymore?

-  if (completed_events_.size() == kMaxClientEvents) {
-    // Don't let the completed events grow beyond the max.
-    completed_events_.pop_front();
-    number_discarded_events_++;
+  // It is possible to get EndConnectionAttempt when there is not an in progress
+  // event, because EndConnectionAttempt is called from SignalConnectionReset,
+  // which will be called any time the network changes state. Only save the
+  // current_event_ if it has data.
+  if (current_event_.has_time_connection_started_ms()) {

[Peter Beverloo, 2017/01/11 14:31:48]

style nit: prefer early return over nesting.

  if (!current_event_.has_time_connection_started_ms())
    return;

[harkness, 2017/01/12 11:04:48]

No longer applicable.

+    if (completed_events_.size() == kMaxClientEvents) {
+      // Don't let the completed events grow beyond the max.
+      completed_events_.pop_front();
+      number_discarded_events_++;
+    }
+
+    // Current event is finished, so add it to our list of completed events.
+    current_event_.set_time_connection_ended_ms(base::Time::Now().ToJavaTime());
+    completed_events_.push_back(current_event_);
+    current_event_.Clear();
   }
-
-  // Current event is now completed, so add it to our list of completed events.
-  current_event_.set_time_connection_ended_ms(base::Time::Now().ToJavaTime());
-  completed_events_.push_back(current_event_);
-  current_event_.Clear();
 }
 
 void ConnectionEventTracker::ConnectionAttemptSucceeded() {