CC: Remove divide from lap-timer.

The divide is surprisingly expensive on Android.

BUG=

Review URL: https://codereview.chromium.org/177193005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254627 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254627