Move RestartUI to CrOSInterface

tools/telemetry/telemetry/core/backends/chrome/cros_interface.py

Index: tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
index edc6f8db86c9d194e1d5b7aaf01ef4809ee184c5..df298e4f5ff90a5f5ae271c3292c334f87caadd3 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
@@ -384,3 +384,15 @@ class CrOSInterface(object):
             screenshot_file])
         return
     logging.warning('screenshot directory full.')
+
+  def RestartUI(self, clear_enterprise_policy):
+    logging.info('(Re)starting the ui (logs the user out)')
+    if clear_enterprise_policy:
+      self.RunCmdOnDevice(['stop', 'ui'])
+      self.RmRF('/var/lib/whitelist/*')
+      self.RmRF('/home/chronos/Local\ State')
+
+    if self.IsServiceRunning('ui'):
+      self.RunCmdOnDevice(['restart', 'ui'])
+    else:
+      self.RunCmdOnDevice(['start', 'ui'])