[graphite] Limit PathAtlas size to max texture size.

In practice I don't think this has come up yet but it may be an issue
as we start using more limited GPUs.

Change-Id: I7d33e18664d7801ac132f4fa54a154f7864b6340
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/815998
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: James Godfrey-Kittle <jamesgk@google.com>
8 files changed