Remove redundant invalidation in RenderLayerModelObject::styleDidChange()

RenderStyle::visualInvalidationDiff() is already returning
'more than enough' paint invalidation flag.
The setShouldDoFullPaintInvalidation() call in
RenderLayerModelObject::styleDidChange() is just redundant.

BUG=349061
TEST=all existing tests pass

Review URL: https://codereview.chromium.org/546513002

git-svn-id: svn://svn.chromium.org/blink/trunk@181480 bbb929c8-8fbe-4397-9dbb-9b2b20218538