[svg] Eliminate an SVGText paint invalidation

NGReplaced called legacy_layout_svg_root->ForceLayout() to ensure legacy
painters' flags had the correct values. But ForceLayout sets
NeedsLayoutForSelf. NeedsLayoutForSelf makes SVG overinvalidate and
consider its viewport size changed. If its viewport size changed,
SVGText children get a MetricsUpdate and forced layout and paint
invalidation, which isn't necessary.

So instead of always calling ForceLayout, we can call LayoutIfNeeded
which doesn't SetNeedsLayoutForSelf.

Fixed: 1235045
Change-Id: I6578c8d074513c21a1ea228d4406b61de8184afd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3069662


Commit-Queue: David Grogan <dgrogan@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#908290}