The layout test fast/text/word-break-keep-all.html that was introduced on <http://trac.webkit.org/r185729> is failing on platform GTK since it was introduced. The diff: https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r185729%20%289361%29/fast/text/word-break-keep-all-diffs.html Possible cause: missing implementation of the feature on platform GTK?
There shouldn't be anything platform-specific about this property. The key changes were in break_lines.h, which is used (AFAIK) by all platforms.