Add cros_debug to kernel commandline in dev images

Every developer image (and test images based on the developer image) should
include "cros_debug" in the kernel commandline. This flag is used by the
crossystem application to determine if the image being run is a developer
image. cros_make_image_bootable receives a new flag, --force_developer_mode
that appends "cros_debug" to the boot args.

BUG=chromium-os:16951
TEST=build images. Flash a base image and confirm the absence of "cros_debug"
in /proc/cmdline. Flash the developer image and confirm the existence of the
string.

Change-Id: I9f748638b5dac384be991908239e8b447ddf3b5e
Reviewed-on: http://gerrit.chromium.org/gerrit/3169
Tested-by: Arkaitz Ruiz Alvarez <arkaitzr@chromium.org>
Reviewed-by: Gaurav Shah <gauravsh@chromium.org>

bin/cros_make_image_bootable

@@ -125,6 +125,9 @@ DEFINE_boolean crosbug12352_arm_kernel_signing ${FLAGS_TRUE} \
 # TODO(sosa):  Remove once known images no longer use this in their config.
 DEFINE_string arm_extra_bootargs "" "DEPRECATED FLAG.  Do not use."
 
+DEFINE_boolean force_developer_mode ${FLAGS_FALSE} \
+  "Add cros_debug to boot args."
+
 # Parse the boot.desc and any overrides
 eval set -- "${BOOT_DESC} ${FLAG_OVERRIDES}"
 FLAGS "${@}" || exit 1
@@ -188,6 +191,10 @@ make_image_bootable() {
     use_dev_keys="--use_dev_keys"
   fi
 
+  if [ ${FLAGS_force_developer_mode} -eq ${FLAGS_TRUE} ]; then
+    FLAGS_boot_args="${FLAGS_boot_args} cros_debug"
+  fi
+
   # Builds the kernel partition image.  The temporary files are kept around
   # so that we can perform a load_kernel_test later on the final image.
   ${SCRIPTS_DIR}/build_kernel_image.sh \

build_image

@@ -487,6 +487,9 @@ update_dev_packages() {
   sudo /sbin/ldconfig -r "${ROOT_FS_DIR}"
 
   # Mark the image as a developer image (input to chromeos_startup).
+  # TODO(arkaitzr): Remove this file when applications no longer rely on it
+  # (crosbug.com/16648). The preferred way of determining developer mode status
+  # is via crossystem cros_debug?1 (checks boot args for "cros_debug").
   sudo mkdir -p "${ROOT_FS_DIR}/root"
   sudo touch "${ROOT_FS_DIR}/root/.dev_mode"
 
@@ -938,7 +941,8 @@ if [ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ] ; then
   update_dev_packages ${DEVELOPER_IMAGE_NAME}
   ${SCRIPTS_DIR}/bin/cros_make_image_bootable "${OUTPUT_DIR}" \
                                               "${DEVELOPER_IMAGE_NAME}" \
-                                              ${crosbug12352_flag}
+                                              ${crosbug12352_flag} \
+                                              --force_developer_mode
 fi
 
 # Create a test or factory test image if desired