[LayoutNG] Add text info to NGPhysicalFragment::ToString()

For when the fragment is NGPhysicalTextFragment.

Bug: 591099
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Idad607ced5a95e836f307b3e88950f0f1ec419ed
Reviewed-on: https://chromium-review.googlesource.com/901082
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534405}
1 file changed