DevTools: Fix console.log for arrays in some corner cases.

We didn't show array values defined on Array.prototype[], as well as non-index property names.

BUG=320632,163817
R=pfeldman

Review URL: https://codereview.chromium.org/143263003

git-svn-id: svn://svn.chromium.org/blink/trunk@165713 bbb929c8-8fbe-4397-9dbb-9b2b20218538