faft: Move and add definitions of GBB flags in FAFTSequence class

Add all the definitions of GBB flags there to make them easy to be used.

BUG=chromium-os:32874
TEST=Run firmware_DevScreenTimeout passed.

Change-Id: I8e6287ccf3e47262467755cb011f8cd1c33977a4
Reviewed-on: https://gerrit.chromium.org/gerrit/28369
Reviewed-by: Vic Yang <victoryang@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 f596d97..c021430 100644
--- a/server/cros/faftsequence.py
+++ b/server/cros/faftsequence.py
@@ -183,6 +183,14 @@
         'US_UNSPECIFIED':     '255', # 0xFF
     }
 
+    # GBB flags
+    GBB_FLAG_DEV_SCREEN_SHORT_DELAY    = 0x00000001
+    GBB_FLAG_LOAD_OPTION_ROMS          = 0x00000002
+    GBB_FLAG_ENABLE_ALTERNATE_OS       = 0x00000004
+    GBB_FLAG_FORCE_DEV_SWITCH_ON       = 0x00000008
+    GBB_FLAG_FORCE_DEV_BOOT_USB        = 0x00000010
+    GBB_FLAG_DISABLE_FW_ROLLBACK_CHECK = 0x00000020
+
     _faft_template = {}
     _faft_sequence = ()