Fix the logic of adding skipped frame.

Bug: n/a
Test: FrameTimelineTest
Change-Id: I21d51d76229701f1fe66982488b5eefedeb02c0c
diff --git a/services/surfaceflinger/FrameTimeline/FrameTimeline.cpp b/services/surfaceflinger/FrameTimeline/FrameTimeline.cpp
index 8369a1e..c8e1fbb 100644
--- a/services/surfaceflinger/FrameTimeline/FrameTimeline.cpp
+++ b/services/surfaceflinger/FrameTimeline/FrameTimeline.cpp
@@ -1166,7 +1166,7 @@
                     (static_cast<float>(mSurfaceFlingerPredictions.presentTime) -
                      kThresh * static_cast<float>(mRenderRate.getPeriodNsecs())) &&
             static_cast<float>(surfaceFrame->getPredictions().presentTime) >=
-                    (static_cast<float>(previousPredictionPresentTime) -
+                    (static_cast<float>(previousPredictionPresentTime) +
                      kThresh * static_cast<float>(mRenderRate.getPeriodNsecs())) &&
             // sf skipped frame is not considered if app is self janked
             !surfaceFrame->isSelfJanky()) {