[LayoutNG] Better legacy static pos computation

layout_ng_block_flow fixes static position computation. It used to be
based on ContainerBlock(), not Container() legacy funcitons expect.

ng_out_of_flow_layout_part() replaces DCHECK with NOTIMPLEMENTED. Since
only 1 remaining test fails with NOTIMPLEMENTED, I am unsure whether
implementation is necessary.

Failing test includes perspective and column width:
compositing/overflow/get-transform-from-non-box-container.html

Bug: 740993
Change-Id: Ia880b923f5fe07521498365efc46380dbb2877c2
Reviewed-on: https://chromium-review.googlesource.com/845142
Commit-Queue: Aleks Totic <atotic@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526274}
2 files changed