input[type=date] warns if specified string is invalid.

We show a console message if:
 - An invalid string is set to 'value' IDL attribute.
 - An invalid string is set to 'value' content attribute.
 - 'date' is set to 'type' attribute and existing 'value' content attribute is
   invalid.
 - 'date' is set to 'type' attribute and existing user-specified value is
   invalid.

BUG=397952
TEST=Update expectations of automated tests.

Review URL: https://codereview.chromium.org/461323006

git-svn-id: svn://svn.chromium.org/blink/trunk@180341 bbb929c8-8fbe-4397-9dbb-9b2b20218538