Restore ShowdowRoot class size in //third_party/blink/renderer/core/dom

The size of ShowdowRoot class had doubled the bitfield size from 16
bits to 32 bits to match the alignment of all compilers after
landing the CL[1]. This CL restores ShowdowRoot class size using
only |unsigned| type with the bitfields.

[1]https://crrev.com/c/1477558/

Bug: 936379
Change-Id: I5faaf4364738835f2fb68036777b148d25bbedc3
Reviewed-on: https://chromium-review.googlesource.com/c/1491743
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636535}
2 files changed