In make_hfs.sh, use `diskutil unmount force` instead of just unmount.

chrome/test/data/safe_browsing/dmg/make_hfs.sh

Index: chrome/test/data/safe_browsing/dmg/make_hfs.sh
diff --git a/chrome/test/data/safe_browsing/dmg/make_hfs.sh b/chrome/test/data/safe_browsing/dmg/make_hfs.sh
index bc478c4ecf8568568ad73220eeee914db415bc75..129dfd0d1b39876e7e29fc96cacdcecee90e79cc 100755
--- a/chrome/test/data/safe_browsing/dmg/make_hfs.sh
+++ b/chrome/test/data/safe_browsing/dmg/make_hfs.sh
@@ -74,6 +74,6 @@ echo "This is a test HFS+ filesystem generated by" \
 popd  # Original PWD
 
 # Unmount the volume, copy the raw device to a file, and then destroy it.
-diskutil unmount ${RAMDISK_VOLUME}
+diskutil unmount force ${RAMDISK_VOLUME}
 dd if=${RAMDISK_VOLUME} of="${OUT_FILE}" &> /dev/null
 diskutil eject ${RAMDISK_VOLUME}