This adds PersistentBase::AnnotateStrongRetainer(const char*) function.

The annotation is used by the heap snapshot generator to show the edges
from the (Global handles) root to the global handles.

Bug: chromium:811842
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I1a9e3e53a53aeaf2b590709fab8dd4ecf7e8f252
Reviewed-on: https://chromium-review.googlesource.com/916788
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51358}