Add Build Timer

Review URL: http://codereview.chromium.org/2859005

build_image

@@ -146,9 +146,6 @@ if [[ -e "$OUTPUT_DIR" ]]; then
   fi
 fi
 
-# Be verbose to help debug failures.
-set -x
-
 # Create the output directory.
 mkdir -p "$OUTPUT_DIR"
 
@@ -577,6 +574,8 @@ if [ "$FLAGS_withdev" -eq "$FLAGS_TRUE" ]; then
   echo "Developer image created as $DEVELOPER_IMAGE_NAME"
 fi
 
+print_time_elapsed
+
 echo "To copy to USB keyfob, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
 echo "To convert to VMWare image, OUTSIDE the chroot, do something like:"

common.sh

@@ -429,3 +429,15 @@ setup_symlinks_on_root() {
 
   sudo ln -s "${var_target}" "${dev_image_root}/var"
 }
+
+# Get current timestamp. Assumes common.sh runs at startup.
+start_time=$(date +%s)
+
+# Print time elsapsed since start_time.
+print_time_elapsed() {
+  end_time=$(date +%s)
+  elapsed_seconds="$(( $end_time - $start_time ))"
+  minutes="$(( $elapsed_seconds / 60 ))"
+  seconds="$(( $elapsed_seconds % 60 ))"
+  echo "Elapsed time: ${minutes}:${seconds}"
+}

mod_image_for_test.sh

@@ -199,5 +199,8 @@ if [ "${VERIFY}" = "true" ]; then
 fi
 
 cleanup
+
+print_time_elapsed
+
 trap - EXIT