[SVG] RenderSVGResourceMarker::layout() should not invalidate dependents

r160730 updated the resource-dependent client invalidation logic to
occur at mutation time, but it missed the layout() override in
RenderSVGResourceMarker - which is still invoking
removeAllClientsFromCache() and may leave nodes in an invalide state at
the end of layout.

The CL aligns RenderSVGResourceMarker's layout() implementation with
the other SVG resources (note that SVGMarkerElement's attribute listener
is already handling the invalidation).

BUG=338461
R=pdr@chromium.org,schenney@chromium.org

Review URL: https://codereview.chromium.org/147903003

git-svn-id: svn://svn.chromium.org/blink/trunk@165901 bbb929c8-8fbe-4397-9dbb-9b2b20218538