Move link prefetch field trial to 2% for m7.
Move link prefetch field trial to 2% for m7.

Per a discussion with laforge & jar, we're backing off in m7 to just
2% field trial on prefetching.

BUG=58046
TEST=nope

Review URL: http://codereview.chromium.org/3608008

git-svn-id: http://src.chromium.org/svn/trunk/src@61564 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: af33d388eab48932f8ee537c2ff1d8bf3e70c3be
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser