This downloads a patched version of jsfunfuzz from google
storage (google internal bucket) as a hook on demand.

Similar to the gcmole approach from
https://codereview.chromium.org/1703533002/

BUG=chromium:535160
LOG=n

Review URL: https://codereview.chromium.org/1706963005

Cr-Commit-Position: refs/heads/master@{#34106}