Do not restrict the visibility of platform only to third_party/WebKit.
Do not restrict the visibility of platform only to third_party/WebKit.

We need to access the unit tests targets from Chromium.

BUG=483171
TEST=gn gen out-gn/Debug
R=dpranke@chromium.org

Review URL: https://codereview.chromium.org/1126433005

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@194954 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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