Change Prefetch Field Trial so the default group is to enable prerender.
Change Prefetch Field Trial so the default group is to enable prerender.

This still leaves a small holdback group for measurement. The advantage is that if someone forgets to bump the Field Trial end date, the behavior will be prerender enabled rather than disabled.

TEST=Set system time later than 06/30/2012 and notice that prerender still works in Chrome


Review URL: http://codereview.chromium.org/8002006

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@102551 0039d316-1c4b-4281-b951-d872f2087c98

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