IndexedDB: Add defaults for switches on WebIDBKeyType (1/4)

Experimental support for "binary" keys is being added to Indexed DB,
which requires extending a type enum. Add 'default:' cases to various
switches on the Chromium side so that the Blink API can be extended.

(This is part 1 of a 4 part landing sequence.)

BUG=297304
R=alecflett@chromium.org

Review URL: https://codereview.chromium.org/25320002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226129 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226129