Add the UMAs for gesture-event based prefetching.
Add the UMAs for gesture-event based prefetching.

Using these UMAs, I want to measure precision/coverage/expected gain when using gesture events as pre-{connect, rendering} trigger.
This is continuation of the work: https://codereview.chromium.org/13902019

BUG=234036

Review URL: https://chromiumcodereview.appspot.com/14708008

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@150250 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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