[Files.app] Simulate a real mouse click in fakeMouseClick in test

Some controls (eg. gear button) watch 'mouseover' and/or 'mouseup' events to see an user clicking, instead of 'click' event. With this patch, fakeMouseClick fires 'mouseover', 'mouseup' and 'mousedown' events before 'click' event so this simulates a real mouse click. This patch is depended by http://crrev.com/128023002/.

BUG=329166
TEST=manually tested

Review URL: https://codereview.chromium.org/134233004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244738 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244738