The fuzz test cases now print the original test paths during execution.
This exploits this extra information and reports a hash of only one
original source file from the section that caused a difference.

The hash size is now limited to 3 to avoid possible duplicate
explosion, in case this doesn't work out as expected.

This prepares for patch 3 of:
https://chromereviews.googleplex.com/550337016/

BUG=chromium:673246
NOTRY=true
TBR=tandrii@chromium.org,mbarbella@chromium.org

Review-Url: https://codereview.chromium.org/2620343005
Cr-Commit-Position: refs/heads/master@{#42305}