HTMLImport: Add test case for workaround import

This patch adds a layout test that confirm no warning if
imported document adds style to the main document by appendChild.

Bug: 523952
Change-Id: Idd5a603d3e585378fc57958969b491d866abf997
Reviewed-on: https://chromium-review.googlesource.com/970046
Reviewed-by: Takayoshi Kochi <kochi@chromium.org>
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547647}
3 files changed