ASSERTION FAILED: x2 >= x1 in WebCore::RenderObject::drawSolidBoxSide

In some cases when a negative margin and a positive padding are applied
together to the right and/or left side of the box, the logical width of
the borders can be set to a negative value, making the assertion fire.
The fix checks if the width or height of the box is negative, and if so,
it will not display the borders and shadows of the box.

This is a backport from WebKit r167351. Patch by Martin Hodovan and reviewed by Darin Adler.

R=schenney@chromium.org
BUG=364797

Review URL: https://codereview.chromium.org/242903002

git-svn-id: svn://svn.chromium.org/blink/trunk@171987 bbb929c8-8fbe-4397-9dbb-9b2b20218538