Use page popup pixel readback for calendar-picker-appearance.html

Use openPickerWithoutMock to test using real page popups and not the iframe mock.

window.internals.pagePopupWindow returns the window object of the page popup.

BUG=409503

Review URL: https://codereview.chromium.org/530653002

git-svn-id: svn://svn.chromium.org/blink/trunk@182909 bbb929c8-8fbe-4397-9dbb-9b2b20218538