[0.11.257.B] Cherry pick crosh dev mode detection to R/M11.

bin/crosh

 #!/bin/dash
 # Copyright (c) 2009-2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 TRY_BASH=1
 if echo "$@" | grep -q -- "--dash"; then
   TRY_BASH=0
 fi
 
@@ skipping 96 matching lines @@
   if ! $CHROMEOS_INSTALL --dst=/dev/null | grep -q "removable"; then
     REMOVABLE=1
   fi
 fi
 
 if [ "$(echo "$@" | grep -- "--usb")" -o "$REMOVABLE" = "1" ]; then
   . "$(dirname "$0")/crosh-usb"
 fi
 
 # TODO(rginda): Switch to the "real" dev mode file when we have one.
-/bin/cros_boot_mode -s -m developer
+/usr/bin/crossystem cros_debug?1
 DEVMODE=$((!$?))
 # Force dev behavior on dev images
-# TODO(wad) replace with a cros_boot_mode arg once supported.
+# TODO(wad,rspangler) replace with a crossystem arg once cros_debug checks this
+# too.
 if [ -f "/root/.dev_mode" ]; then
   DEVMODE=1
 fi
 
 if [ "$(echo "$@" | grep -- "--dev")" -o "$DEVMODE" = "1" ]; then
   . "$(dirname "$0")/crosh-dev"
 fi
 
 if [ -e "$(dirname $0)/crosh-workarounds" ]; then
   . "$(dirname "$0")/crosh-workarounds"
@@ skipping 372 matching lines @@
   done
 }
 
 INPUTRC="$(dirname "$0")/inputrc.crosh"
 HISTFILE="$HOME/.crosh_history"
 shell_history -r $HISTFILE
 
 repl
 
 shell_history -w $HISTFILE