Remove unnecessary assertions which was added accidentally in the previous CL.
Remove unnecessary assertions which was added accidentally in the previous CL.

The previous CL, https://codereview.chromium.org/1086873002/, added this assertion, [1], accidentally.

[1]: https://codereview.chromium.org/1086873002/diff/40001/Source/core/dom/LayoutTreeBuilderTraversal.cpp#newcode57.

BUG=472973,477161

Review URL: https://codereview.chromium.org/1089553002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@193834 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,Pluto-tv/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,smishenk/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,smishenk/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,Pluto-tv/blink-crosswalk,smishenk/blink-crosswalk,Pluto-tv/blink-crosswalk,XiaosongWei/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,Pluto-tv/blink-crosswalk,PeterWangIntel/blink-crosswalk,Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk