Adding a preloadScanner watch list, and adding myself

I'm interested in following up changes to the preloadScanner and to prerender.
Therefore, I created a preloadScanner WatchList rule, added myself to it and to the prerender watchlist.

Review URL: https://codereview.chromium.org/571083002

git-svn-id: svn://svn.chromium.org/blink/trunk@182003 bbb929c8-8fbe-4397-9dbb-9b2b20218538