Use new grub2 variables to boot from the device with the bootloader

src/platform/installer/chromeos-common.sh

Index: src/platform/installer/chromeos-common.sh
diff --git a/src/platform/installer/chromeos-common.sh b/src/platform/installer/chromeos-common.sh
index c26c42d3a2fcff94714fdd1327d59ac50889bf10..5283145a87bacdffe340226a4060567a97e3eeda 100644
--- a/src/platform/installer/chromeos-common.sh
+++ b/src/platform/installer/chromeos-common.sh
@@ -486,3 +486,15 @@ make_arm_mbr() {
   fi
   echo ${MBR_SCRIPT_UIMG}
 }
+
+
+# The scripts that source this file typically want to use the root password as
+# confirmation, unless the --run_as_root flag is given.
+dont_run_as_root() {
+  if [ $(id -u) -eq "0" -a "${FLAGS_run_as_root}" -eq "${FLAGS_FALSE}" ]
+  then
+    echo "Note: You must be the 'chronos' user to run this script. Unless"
+    echo "you pass --run_as_root and run as root."
+    exit 1
+  fi
+}