Change prerender control group to be observe-prefetch-without-actually-prefetching.
Change prerender control group to be observe-prefetch-without-actually-prefetching.

Also, drop prefetch probability to 0%.

BUG=None
TEST=None

Review URL: http://codereview.chromium.org/6621044

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@77230 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser