tracing: ensure __metadata events are always added to the trace

base/trace_event/trace_event_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/trace_event/trace_event.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 3101 matching lines @@
   config1.Merge(config2);
   EXPECT_EQ(2u, config1.GetSyntheticDelayValues().size());
 }
 
 TEST_F(TraceEventTestFixture, SyntheticDelayConfigurationToString) {
   const char filter[] = "DELAY(test.Delay;16;oneshot)";
   TraceConfig config(filter, "");
   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