[SfStats] Record vsync event connection count

Bug: 135480141
Test: ./statsd_testdrive 10062
Change-Id: I220f0c96935c96afea194ed8ca69922785cf296e
diff --git a/services/surfaceflinger/Scheduler/EventThread.h b/services/surfaceflinger/Scheduler/EventThread.h
index 641b2a5..466234d 100644
--- a/services/surfaceflinger/Scheduler/EventThread.h
+++ b/services/surfaceflinger/Scheduler/EventThread.h
@@ -16,7 +16,12 @@
 
 #pragma once
 
+#include <android-base/thread_annotations.h>
+#include <gui/DisplayEventReceiver.h>
+#include <gui/IDisplayEventConnection.h>
+#include <private/gui/BitTube.h>
 #include <sys/types.h>
+#include <utils/Errors.h>
 
 #include <condition_variable>
 #include <cstdint>
@@ -26,13 +31,6 @@
 #include <thread>
 #include <vector>
 
-#include <android-base/thread_annotations.h>
-
-#include <gui/DisplayEventReceiver.h>
-#include <gui/IDisplayEventConnection.h>
-#include <private/gui/BitTube.h>
-
-#include <utils/Errors.h>
 #include "HwcStrongTypes.h"
 
 // ---------------------------------------------------------------------------
@@ -134,6 +132,9 @@
     // Usage of this method assumes that only the primary internal display
     // supports multiple display configurations.
     virtual void requestLatestConfig() = 0;
+
+    // Retrieves the number of event connections tracked by this EventThread.
+    virtual size_t getEventThreadConnectionCount() = 0;
 };
 
 namespace impl {
@@ -168,6 +169,8 @@
 
     void setPhaseOffset(nsecs_t phaseOffset) override;
 
+    size_t getEventThreadConnectionCount() override;
+
 private:
     friend EventThreadTest;