Add default testing command line flags in UITestBase instead of ProxyLauncher.

chrome/test/ui/ui_test.cc

Index: chrome/test/ui/ui_test.cc
diff --git a/chrome/test/ui/ui_test.cc b/chrome/test/ui/ui_test.cc
index 9ee6ead42770e42aea41fedb088767a2832071ab..2128b9dbc2d92b76a124cb7d2b15f555d4e20ce4 100644
--- a/chrome/test/ui/ui_test.cc
+++ b/chrome/test/ui/ui_test.cc
@@ -46,6 +46,7 @@
 #include "chrome/test/automation/window_proxy.h"
 #include "chrome/test/base/chrome_process_util.h"
 #include "chrome/test/base/testing_profile.h"
+#include "chrome/test/base/test_launcher_utils.h"
 #include "chrome/test/base/test_switches.h"
 #include "content/common/debug_flags.h"
 #include "googleurl/src/gurl.h"
@@ -175,6 +176,9 @@ void UITestBase::SetLaunchSwitches() {
   // chrome/test/pyautolib/pyauto.py as well to take effect for all tests
   // on chromeos.
 
+  // Propagate commandline settings from test_launcher_utils.
+  test_launcher_utils::PrepareBrowserCommandLineForTests(&launch_arguments_);
+
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kWaitForDebugger))
     launch_arguments_.AppendSwitch(switches::kWaitForDebugger);