Add trace-to-file support for base::TestSuite

base/debug/trace_to_file.h

Index: base/debug/trace_to_file.h
diff --git a/base/debug/trace_to_file.h b/base/debug/trace_to_file.h
new file mode 100644
index 0000000000000000000000000000000000000000..a75307e0a3c88d24ef3a8443f84f512ec7c217f4
--- /dev/null
+++ b/base/debug/trace_to_file.h
@@ -0,0 +1,38 @@
+// Copyright (c) 2014 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 BASE_DEBUG_TRACE_TO_FILE_H_
+#define BASE_DEBUG_TRACE_TO_FILE_H_
+
+#include "base/files/file_path.h"
+
+namespace base {
+namespace debug {
+
+class TraceToFile {
+ public:
+  TraceToFile();
+  ~TraceToFile();
+
+  void BeginTracingFromCommandLineOptions();
+  void BeginTracing(const base::FilePath& path, const std::string& categories);
+
+  // Assumes current message loop is not being pumped and is idle.
+  // This is a valid assumption for unit tests, but not for the browser.
+  void EndTracingIfNeeded();
+
+ private:
+  void WriteFileHeader();
+  void AppendFileFooter();
+
+  void TraceOutputCallback(const std::string& data);
+
+  base::FilePath path_;
+  bool started_;
+};
+
+}  // namespace debug
+}  // namespace base
+
+#endif  // BASE_DEBUG_TRACE_TO_FILE_H_