DevTools: Show entries for ES6 Map, Set, WeakMap and WeakSet in console.

BUG=376196
R=yurys

Review URL: https://codereview.chromium.org/509513002

git-svn-id: svn://svn.chromium.org/blink/trunk@180983 bbb929c8-8fbe-4397-9dbb-9b2b20218538