Tune the delay of entering recovery mode in FAFT.

A previous CL changed the firmware screen delay from 10s to 2s.
https://gerrit.chromium.org/gerrit/14140
But when entering recovery mode, the firmware first reads the kernel in
the low-speed USB disk. As a result, 2s is not enough. This CL tunes the
delay of entering recovery mode.

BUG=chromium-os:19710
TEST=run_remote_tests.sh --remote=$REMOTE_IP -a "xml_config=$OVERLAY_XML \
        servo_serial=$SERIAL" firmware_FwScreenCloseLid
     run_remote_tests.sh --remote=$REMOTE_IP -a "xml_config=$OVERLAY_XML \
        servo_serial=$SERIAL" firmware_FwScreenPressPower

Change-Id: I28dc468aac2989ca8940a6503c58ac5a51558347
Reviewed-on: https://gerrit.chromium.org/gerrit/15372
Reviewed-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/faftsequence.py b/server/cros/faftsequence.py
index 8fbcc46..d047205 100644
--- a/server/cros/faftsequence.py
+++ b/server/cros/faftsequence.py
@@ -82,10 +82,15 @@
     OTHER_KERNEL_MAP = {'a':'4', 'b':'2', '2':'4', '4':'2', '3':'4', '5':'2'}
     OTHER_ROOTFS_MAP = {'a':'5', 'b':'3', '2':'5', '4':'3', '3':'5', '5':'3'}
 
-    # Delay timing
+    # Delay between power-on and firmware screen.
     FIRMWARE_SCREEN_DELAY = 2
+    # Delay between passing firmware screen and text mode warning screen.
     TEXT_SCREEN_DELAY = 20
+    # Delay of loading the USB kernel.
+    USB_LOAD_DELAY = 5
+    # Delay between USB plug-out and plug-in.
     USB_PLUG_DELAY = 10
+    # Delay after running the 'sync' command.
     SYNC_DELAY = 5
 
     CHROMEOS_MAGIC = "CHROMEOS"
@@ -497,7 +502,7 @@
 
     def wait_fw_screen_and_plug_usb(self):
         """Wait for firmware warning screen and then unplug and plug the USB."""
-        time.sleep(self.FIRMWARE_SCREEN_DELAY)
+        time.sleep(self.USB_LOAD_DELAY)
         self.servo.set('usb_mux_sel1', 'servo_sees_usbkey')
         time.sleep(self.USB_PLUG_DELAY)
         self.servo.set('usb_mux_sel1', 'dut_sees_usbkey')