Add [TypeChecking=Interface] to Animation interface

This affects its constructor, which takes a (nullable) Element argument,
and with this change throws a TypeError if the argument value is not null,
undefined or an element. Previously it would treat all non-element values
as null.

BUG=462561

Review URL: https://codereview.chromium.org/962963008

git-svn-id: svn://svn.chromium.org/blink/trunk@191532 bbb929c8-8fbe-4397-9dbb-9b2b20218538
1 file changed