[SVG] Transform animation leaves traces of text behind.

AffineTransform.inverse() unexpectedly returned an identity matrix when
the matrix was not invertible. This caused invalid rendering for e.g
scale(0) matrices in svg.

BUG=352603

Review URL: https://codereview.chromium.org/200053005

git-svn-id: svn://svn.chromium.org/blink/trunk@169666 bbb929c8-8fbe-4397-9dbb-9b2b20218538