Added '--help' switch to display WD usage

Author: Mykola Tryshnivskyy

src/chrome/test/webdriver/webdriver_server.cc

@@ -328,6 +328,33 @@ int RunChromeDriver() {
   base::WaitableEvent shutdown_event(false, false);
   CommandLine* cmd_line = CommandLine::ForCurrentProcess();
 
+  // check if --help CL argument is present
+  if (cmd_line->HasSwitch("help")) {
+    std::cout << "Usage: WebDriver [--OPTION=VALUE]..."                                             << std::endl
+              << "Starts WebDriver server"                                                          << std::endl
+              << ""                                                                                 << std::endl
+              << "OPTION         DEFAULT VALUE      DESCRIPTION"                                    << std::endl
+              << "http-threads   4                  The number of threads to use for handling"      << std::endl
+              << "                                  HTTP requests"                                  << std::endl
+              << "log-path       ./webdriver.log    The path to use for the ChromeDriver server"    << std::endl
+              << "                                  log"                                            << std::endl
+              << "root           ./web              The path of location to serve files from"       << std::endl
+              << "port           9517               The port that ChromeDriver listens on"          << std::endl
+              << "silence        false              If true, ChromeDriver will not log anything"    << std::endl
+              << "                                  to stdout/stderr"                               << std::endl
+              << "verbose        false              If true, ChromeDriver will log lots of stuff"   << std::endl
+              << "                                  to stdout/stderr"                               << std::endl
+              << "url-base                          The URL path prefix to use for all incoming"    << std::endl
+              << "                                  WebDriver REST requests. A prefix and postfix"  << std::endl
+              << "                                  '/' will automatically be appended if not"      << std::endl
+              << "                                  present"                                        << std::endl
+              << "config                            The path to config file (e.g. config.json) in"  << std::endl
+              << "                                  JSON format with specified WD parameters as"    << std::endl
+              << "                                  described above (port, root, etc.)"             << std::endl;
+
+     return (EXIT_SUCCESS);
+  }
+
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
   // set default output mode
   qInstallMessageHandler(normalMessageOutput);