Once WebCore stops using an exports file, the default visibility of ANGLE symbols will carry over to WebCore. WebCore shouldn’t export any ANGLE symbols, so ANGLE should build with -fvisibility=hidden.
Created attachment 243729 [details] Change GCC_SYMBOLS_PRIVATE_EXTERN to YES
Note that there are important steps to take when updating ANGLE. See http://trac.webkit.org/wiki/UpdatingANGLE
Fixed in <http://trac.webkit.org/r177724>.