[LayoutNG] Add DHECK of CanUseInlineBox() in ContainerNode.cpp

ContainerNode::GetUpperLeftCorner() uses legacy inline structures, which
will be removed when LayoutNG is enabled. This patch adds a DCHECK to
ease the tracking of the conversion of existing usage of legacy inline
structures.

Bug: 591099
Change-Id: Idac4b13a590e9799affe1f5a34726ecc7f7f1bab
Reviewed-on: https://chromium-review.googlesource.com/769567
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516824}
2 files changed