Implicit references reported to V8 with V8::AddImplicitReferences calls are now reported by heap profiler as 'native' references with type kInternal.

Original WebKit bug report: https://bugs.webkit.org/show_bug.cgi?id=77414
Review URL: https://chromiumcodereview.appspot.com/9316092

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10603 ce2b1a6d-e550-0410-aec6-3dcde31c8c00