Because C++ API of ICU 4.8 is not upper-compatible with ICU 4.6.
Created attachment 131285 [details] Patch
Comment on attachment 131285 [details] Patch Looks good.
Comment on attachment 131285 [details] Patch Clearing flags on attachment: 131285 Committed r110414: <http://trac.webkit.org/changeset/110414>
All reviewed patches have been landed. Closing bug.