Reland [Startup Tracing] Add --trace-config-file flag

components/tracing/startup_tracing.h

Index: components/tracing/startup_tracing.h
diff --git a/components/tracing/startup_tracing.h b/components/tracing/startup_tracing.h
deleted file mode 100644
index 5d1c74d05c19e1f222b1fe844ec57bf60b15f5a2..0000000000000000000000000000000000000000
--- a/components/tracing/startup_tracing.h
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright (c) 2015 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.
-
-#ifndef COMPONENTS_TRACING_STARTUP_TRACING_H_
-#define COMPONENTS_TRACING_STARTUP_TRACING_H_
-
-#include "components/tracing/tracing_export.h"
-
-namespace tracing {
-
-// Enable startup tracing according to the trace config file. If the trace
-// config file does not exist, it will do nothing. This is designed to be used
-// by Telemetry. Telemetry will stop tracing via DevTools later. To avoid
-// conflict, this should not be used when --trace-startup is enabled.
-void TRACING_EXPORT EnableStartupTracingIfConfigFileExists();
-
-}  // namespace tracing
-
-#endif  // COMPONENTS_TRACING_STARTUP_TRACING_H_