[ChromeDriver] Subscribe PerformanceLogger to CommandListener interface

chrome/test/chromedriver/command_listener.h

+// Copyright 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 CHROME_TEST_CHROMEDRIVER_COMMAND_LISTENER_H_
+#define CHROME_TEST_CHROMEDRIVER_COMMAND_LISTENER_H_
+
+#include <string>
+
+class Status;
+
+class CommandListener {
+ public:
+  virtual ~CommandListener() {}
+
+  // Called just before a WebDriver command is run, but only
+  // for commands that operate on an existing session. Will be called for
+  // WindowCommands, ElementCommands, SessionCommands, and AlertCommands.
+  virtual Status BeforeCommand(const std::string& command_name) = 0;
+};
+
+#endif  // CHROME_TEST_CHROMEDRIVER_COMMAND_LISTENER_H_