Unapply effectiveZoom during SVG layout

Text layout in SVG is assumed to happen in unzoomed coordinates.
Prior to this patch, there was a special SVG mode in the
StyleResolver that disregarded zoom when resolving lengths for
SVG elements. That broke down during inheritance though, so a
better way to handle the SVG zoom model is for the SVG module to
remove zoom from style values itself.

BUG=382366

Review URL: https://codereview.chromium.org/323053002

git-svn-id: svn://svn.chromium.org/blink/trunk@176051 bbb929c8-8fbe-4397-9dbb-9b2b20218538