Revert "Workaround for the Tern crash."

This reverts commit 22fed2a8e230f07394b3b1b5dfb8691dd214d76f, which is no longer needed in Chromium 29.

**DO NOT MERGE UNTIL adobe/brackets-shell#287 IS MERGED!**

Note: you will need to run `git submodule sync` after pulling these changes, since the acorn submodule URL is changed back to marijn's repo.