Get rid of Isolate::safe_stack_iterator_counter
This change removes per-isolate counter of active SafeStackFrameIterators. The counter is used by stack frames implementations to avoid accessing pointers to heap objects when traversing stack for CPU profiler (so called "safe" mode). Each StackFrame instance is owned by single iterator and has a pointer to it so we can simply mark the iterator as "safe" or not and read the field in the stack frames instead of going into the isolate.
BUG=None
R=loislo@chromium.org, svenpanne@chromium.org
Review URL: https://codereview.chromium.org/
17585008
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15317
ce2b1a6d-e550-0410-aec6-
3dcde31c8c00