HeapProfiler: for the test purposes we would like to trace object movements.

When we have an untracked allocations we need to fix it.
It is a bit tricky process due to lack of logging.

I added FLAG_heap_profiler_trace_objects that enables log for object movements.

Drive by fix: with help of logging I found a bug in LeftTrim method for FixedArray.

BUG=none
R=svenpanne@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/27694004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17258 ce2b1a6d-e550-0410-aec6-3dcde31c8c00