[GridNG] Fix subgrid-baseline-002.html

Previously when synthesizing baselines we'd potentially use two
different FontBaseline (which determine whether to synthesize off the
block-end edge, or the middle).

This patch passes in the parent_grid_style such that we consistently
use the parent's FontBaseline when synthesizing.

Bug: 618969
Change-Id: Ib923e9c489039af2811c13563002801b5e2f686d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4583538
Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Reviewed-by: Ethan Jimenez <ethavar@microsoft.com>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1157228}