[PATCH] [asan] Make ASan report the correct thread address ranges to LSan.

[Sergey Matveev]

  It turns out that this change causes problems with Chrome's sandbox, because of the arch_prctl call in GetThreadStackAndTls.

  We could avoid calling arch_prctl if we obtain the $fs value from the thread descriptor itself (glibc stores it at something like $fs:4). By doing so we would introduce another assumption about glibc internals (but we already have one about thread descriptor size, so it's not that big of a deal). In fact, arch_prctl is not supported on i386, so we would have to do that for i386 either way. In this light, don't see any reason to keep clinging to arch_prctl on x86_64.

  What does everyone think?

http://llvm-reviews.chandlerc.com/D862