Always aligns text at vertically center (Textfield, Label).

This CL makes Textfield and Label put their content text at vertically center respecting the cap height.

Also this CL removes vertical alignment support, which we no longer need.

I think this CL fixes all issues related to vertical alignment and font height.

BUG=146236, 264436
TEST=Test manually + ui_unittests

Review URL: https://codereview.chromium.org/25039002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231107 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231107