[LayoutNG] Fix inline out-of-flow container computation

The out-of-flow code assumed that all fragments for a
LayoutInline has the same height, but the change for
crbug.com/903578 (WIP CL:1251142) breaks the assumption.

This patch fixes by computing the rect and uniting them,
instead of taking the max of heights.

No behavior changes until the WIP CL lands.

Change-Id: I9fe6b35d25836fde10dd88dd90ca2a810f5c9863
Bug: 636993, 903578
Reviewed-on: https://chromium-review.googlesource.com/c/1351189
Reviewed-by: Aleks Totic <atotic@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610994}
3 files changed