Dump last committed vSyncId on layers trace start

Keep track of the last committed vSyncId to dump it when we start the layers trace

Bug: 230462538

Test: Check a vSyncId is dumped in the first entry of the layers trace
Change-Id: Ie4c48acf99057cdb8bfebbf5cea3729ab5014bd4
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 41de2b6..ca4de73 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1266,6 +1266,8 @@
     const std::unique_ptr<FrameTracer> mFrameTracer;
     const std::unique_ptr<frametimeline::FrameTimeline> mFrameTimeline;
 
+    int64_t mLastCommittedVsyncId = -1;
+
     // If blurs should be enabled on this device.
     bool mSupportsBlur = false;
     // If blurs are considered expensive and should require high GPU frequency.