diff -r 000000000000 -r 6474c204b198 toolkit/devtools/acorn/UPGRADING.md
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/acorn/UPGRADING.md	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,28 @@
+Assuming that acorn's dependencies have not changed, to upgrade our tree's
+acorn to a new version:
+
+1. Clone the acorn repository, and check out the version you want to upgrade
+to:
+
+       $ git clone https://github.com/marijnh/acorn.git
+       $ cd acorn
+       $ git checkout <version>
+
+2. Make sure that all tests pass:
+
+       $ npm install .
+       $ npm test
+
+   If there are any test failures, do not upgrade to that version of acorn!
+
+3. Copy acorn.js to our tree:
+
+       $ cp acorn.js /path/to/mozilla-central/toolkit/devtools/acorn/acorn.js
+
+4. Copy acorn_loose.js to our tree:
+
+       $ cp acorn_loose.js /path/to/mozilla-central/toolkit/devtools/acorn/acorn_loose.js
+
+5. Copy util/walk.js to our tree:
+
+       $ cp util/walk.js /path/to/mozilla-central/toolkit/devtools/acorn/walk.js