faft: Support SPACE key to trigger TO_NORM screen

We changed the key for triggering TO_NORM screen from ENTER to SPACE.
This change adds:
 - the logic of supporting the alternative of space (ctrl+f3) on servo;
 - custromized space command instead of using servo;
 - sending both SPACE and ENTER to trigger TO_NORM screen.

BUG=chrome-os-partner:12057
TEST=Run firmware_DevMode on Snow passed.

Change-Id: Ied9242c2484e0172e3cbe83ed7f6659a3afce0fe
Reviewed-on: https://gerrit.chromium.org/gerrit/28929
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/servo.py b/server/cros/servo.py
index 53d2a06..3205cec 100644
--- a/server/cros/servo.py
+++ b/server/cros/servo.py
@@ -243,6 +243,14 @@
         self._press_and_release_keys('none', 'refresh')
 
 
+    def ctrl_refresh_key(self):
+        """Simulate Ctrl and Refresh (F3) simultaneous press.
+
+        This key combination is an alternative of Space key.
+        """
+        self._press_and_release_keys('ctrl_r', 'refresh')
+
+
     def imaginary_key(self):
         """Simulate imaginary key button press.