[chromedriver] Pass --test-type=webdriver when launching Chrome

chrome/test/chromedriver/chrome_launcher.cc

Index: chrome/test/chromedriver/chrome_launcher.cc
diff --git a/chrome/test/chromedriver/chrome_launcher.cc b/chrome/test/chromedriver/chrome_launcher.cc
index 539c18c3f14a3646b8fcb9c01050c2a1ffe8c386..7b585b0ac901810a39675f069c3da8f20053cc22 100644
--- a/chrome/test/chromedriver/chrome_launcher.cc
+++ b/chrome/test/chromedriver/chrome_launcher.cc
@@ -116,6 +116,7 @@ Status PrepareCommandLine(int port,
   switches.SetSwitch("password-store", "basic");
   switches.SetSwitch("use-mock-keychain");
   switches.SetSwitch("remote-debugging-port", base::IntToString(port));
+  switches.SetSwitch("test-type", "webdriver");
 
   for (std::set<std::string>::const_iterator iter =
            capabilities.exclude_switches.begin();