- Remove unneeded include of ucontext.h as it is deprecated on Snow Leopard. - Avoid calculating shared library addresses if profiling is not enabled.
- Remove unneeded include of ucontext.h as it is deprecated on Snow Leopard.
- Avoid calculating shared library addresses if profiling is not enabled.

Review URL: http://codereview.chromium.org/155814

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@2517 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh