[SfStats] Record vsync event connection count

Bug: 135480141
Test: ./statsd_testdrive 10062
Change-Id: I220f0c96935c96afea194ed8ca69922785cf296e
diff --git a/services/surfaceflinger/Scheduler/EventThread.cpp b/services/surfaceflinger/Scheduler/EventThread.cpp
index 14e3ec6..acab5a6 100644
--- a/services/surfaceflinger/Scheduler/EventThread.cpp
+++ b/services/surfaceflinger/Scheduler/EventThread.cpp
@@ -335,6 +335,11 @@
     mCondition.notify_all();
 }
 
+size_t EventThread::getEventThreadConnectionCount() {
+    std::lock_guard<std::mutex> lock(mMutex);
+    return mDisplayEventConnections.size();
+}
+
 void EventThread::threadMain(std::unique_lock<std::mutex>& lock) {
     DisplayEventConsumers consumers;