tracing: ensure __metadata events are always added to the trace

base/trace_event/trace_event_unittest.cc

Index: base/trace_event/trace_event_unittest.cc
diff --git a/base/trace_event/trace_event_unittest.cc b/base/trace_event/trace_event_unittest.cc
index 25a6d5f3f6213508b9fcc838179038a597252ec1..e2597d106bcdef8d3fd8d05a18668fc039f3809c 100644
--- a/base/trace_event/trace_event_unittest.cc
+++ b/base/trace_event/trace_event_unittest.cc
@@ -3119,5 +3119,12 @@ TEST_F(TraceEventTestFixture, SyntheticDelayConfigurationToString) {
   EXPECT_EQ(filter, config.ToCategoryFilterString());
 }
 
+TEST_F(TraceEventTestFixture, ClockSyncEventsAreAlwaysAddedToTrace) {
+  BeginSpecificTrace("-*");
+  TRACE_EVENT_CLOCK_SYNC_RECEIVER(1);
+  EndTraceAndFlush();
+  EXPECT_TRUE(FindNamePhase("clock_sync", "c"));
+}
+
 }  // namespace trace_event
 }  // namespace base