Implemented "no heap access" mode for JSFrame which is used for stack sampling in...

Implemented "no heap access" mode for JSFrame which is used for stack sampling in profiler.

As I discovered that JSFrame accesses SharedFunctionInfo only to calculate caller SP and the latter is not used in profiler's stack sampling, I disabled accessing heap objects in JSFrame when doing stack sampling. This finally made V8's profiling stable when used from Chrome on a real web app.

Review URL: http://codereview.chromium.org/73020

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1694 ce2b1a6d-e550-0410-aec6-3dcde31c8c00