Fix a bug in heap profile tracing of closures.

Fix a bug in heap profile tracing of closures.

The heap profile tracers assumed that a closure always closed over a
function context.  This is obviously not true (e.g., function expressions
nested inside catch or with).  This assumption could lead to using a
function's scope info to interpret a catch or with context.

R=vegorov@chromium.org
BUG=v8:2078
TEST=

Review URL: https://chromiumcodereview.appspot.com/9969198

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11348 ce2b1a6d-e550-0410-aec6-3dcde31c8c00