GitLab

Move this !ENABLE(INPUT_MULTIPLE_FIELDS_UI) object to the Oilpan heap,
where it belongs as it derives from the on-heap BaseDateAndTimeInputType
class.

At the same time, turn DateTimeChooserClient into a GC mixin.

R=haraken
BUG=553613

Review URL: https://codereview.chromium.org/1466113002

Cr-Commit-Position: refs/heads/master@{#361071}