Remove the last SVG callers of bloatedCharacters

This CL removes the calls to bloatedCharacters from SVGTextLayoutEngine and
SVGTextLayoutAttributesBuilder. Originally, these call sites looked scary to
me, but they turned out to be fairly straightforward.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/19520011

git-svn-id: svn://svn.chromium.org/blink/trunk@154539 bbb929c8-8fbe-4397-9dbb-9b2b20218538