Now that Map just contains a pointer, and is passed by value to
Logger::MapDetails, printing the this pointer in Map::PrintMapDetails no longer
makes sense, but we need to print the underlying pointer.

BUG=v8:3770

Change-Id: I87f41c796dbff7a8800731bb1d63a7482b9ff71c
Reviewed-on: https://chromium-review.googlesource.com/c/1347485Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57733}