SF: don't trace SF timelines when there is no layer update

Fixes: 239101875
Test: manual
Change-Id: I024f6facff5d74a500fb5d917bd97ab5d1c3eba3
diff --git a/services/surfaceflinger/tests/unittests/FrameTimelineTest.cpp b/services/surfaceflinger/tests/unittests/FrameTimelineTest.cpp
index f47ac6d..abd7789 100644
--- a/services/surfaceflinger/tests/unittests/FrameTimelineTest.cpp
+++ b/services/surfaceflinger/tests/unittests/FrameTimelineTest.cpp
@@ -44,6 +44,17 @@
 
 namespace android::frametimeline {
 
+static const std::string sLayerNameOne = "layer1";
+static const std::string sLayerNameTwo = "layer2";
+
+constexpr const uid_t sUidOne = 0;
+constexpr pid_t sPidOne = 10;
+constexpr pid_t sPidTwo = 20;
+constexpr int32_t sInputEventId = 5;
+constexpr int32_t sLayerIdOne = 1;
+constexpr int32_t sLayerIdTwo = 2;
+constexpr GameMode sGameMode = GameMode::Unsupported;
+
 class FrameTimelineTest : public testing::Test {
 public:
     FrameTimelineTest() {
@@ -106,6 +117,14 @@
         return packets;
     }
 
+    void addEmptySurfaceFrame() {
+        auto surfaceFrame =
+                mFrameTimeline->createSurfaceFrameForToken({}, sPidOne, sUidOne, sLayerIdOne,
+                                                           sLayerNameOne, sLayerNameOne,
+                                                           /*isBuffer*/ false, sGameMode);
+        mFrameTimeline->addSurfaceFrame(std::move(surfaceFrame));
+    }
+
     void addEmptyDisplayFrame() {
         auto presentFence1 = fenceFactory.createFenceTimeForTest(Fence::NO_FENCE);
         // Trigger a flushPresentFence by calling setSfPresent for the next frame
@@ -168,17 +187,6 @@
                                                                   kStartThreshold};
 };
 
-static const std::string sLayerNameOne = "layer1";
-static const std::string sLayerNameTwo = "layer2";
-
-constexpr const uid_t sUidOne = 0;
-constexpr pid_t sPidOne = 10;
-constexpr pid_t sPidTwo = 20;
-constexpr int32_t sInputEventId = 5;
-constexpr int32_t sLayerIdOne = 1;
-constexpr int32_t sLayerIdTwo = 2;
-constexpr GameMode sGameMode = GameMode::Unsupported;
-
 TEST_F(FrameTimelineTest, tokenManagerRemovesStalePredictions) {
     int64_t token1 = mTokenManager->generateTokenForPredictions({0, 0, 0});
     EXPECT_EQ(getPredictions().size(), 1u);
@@ -1054,6 +1062,9 @@
     auto presentFence1 = fenceFactory.createFenceTimeForTest(Fence::NO_FENCE);
 
     tracingSession->StartBlocking();
+
+    // Add an empty surface frame so that display frame would get traced.
+    addEmptySurfaceFrame();
     int64_t displayFrameToken1 = mTokenManager->generateTokenForPredictions({10, 30, 30});
 
     // Set up the display frame
@@ -1135,6 +1146,9 @@
     // Flush the token so that it would expire
     flushTokens();
 
+    // Add an empty surface frame so that display frame would get traced.
+    addEmptySurfaceFrame();
+
     // Set up the display frame
     mFrameTimeline->setSfWakeUp(displayFrameToken1, 20, Fps::fromPeriodNsecs(11));
     mFrameTimeline->setSfPresent(26, presentFence1);