Fix TraceEventTestFixture flakiness

base/debug/trace_event_unittest.h

Index: base/debug/trace_event_unittest.h
diff --git a/base/test/mock_devices_changed_observer.cc b/base/debug/trace_event_unittest.h
similarity index 53%
copy from base/test/mock_devices_changed_observer.cc
copy to base/debug/trace_event_unittest.h
index c05f26a61382ddbbe2429a70f6490554917cff3b..3b570e1ca26752d15a4f10ac7a163ffacaba5e44 100644
--- a/base/test/mock_devices_changed_observer.cc
+++ b/base/debug/trace_event_unittest.h
@@ -2,14 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/test/mock_devices_changed_observer.h"
+#include "base/time.h"
 
 namespace base {
+namespace debug {
 
-MockDevicesChangedObserver::MockDevicesChangedObserver() {
-}
-
-MockDevicesChangedObserver::~MockDevicesChangedObserver() {
-}
+// Sleep until HighResNow has advanced by at least |elapsed|.
+void HighResSleepForTraceTest(base::TimeDelta elapsed);
 
+}  // namespace debug
 }  // namespace base