Disable three DomSerializerTests in preperation of page serializer merge

This CL fixes my mistake in https://codereview.chromium.org/115163002/ where
I prepended the tests with 'DISABLE_' instead of 'DISABLED_'. It also disables
one additional test that will not work due to the merge.

R=jochen
BUG=328354

Review URL: https://codereview.chromium.org/106023004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241545 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241545