Removing base::Time from SetAnimationEvents and PostAnimationEventsToMainThreadOnImplThread.

As of "Remove wall time from NotifyAnimationStarted and NotifyAnimationFinished"
(https://src.chromium.org/viewvc/chrome?view=rev&revision=255888) the wall time
is no longer used in either of these functions.

BUG=299945

Review URL: https://codereview.chromium.org/194543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256237 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256237