This is the default for x86, but not the default for arm64. This means on arm64 we don't be able to unwind past C/C++ frames on arm64 unless we compile with this flag.
<rdar://problem/63104244>
Created attachment 399089 [details] patch
Note that there are important steps to take when updating ANGLE. See http://trac.webkit.org/wiki/UpdatingANGLE
We're not going to do this. If we encounter more bugs in the future where this behavior matters, we'd probably choose to align behavior instead on -fno-unwind-tables. And fix bad users relying on unwinding from calling into C API.