Remove Views find bar textfield border.

The border is not needed for painting or sizing.
It also causes an ugly solid color border on CrOS.
Fixes a regression from r244436 and r244746.

BUG=335346
TEST=The find bar looks as expected on Views.
R=sky@chromium.org

Review URL: https://codereview.chromium.org/142193002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245821 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245821