DevTools: Some printed objects in console are not pinnable.

For example: console.log(new Date)

BUG=327109
R=pfeldman

Review URL: https://codereview.chromium.org/297163014

git-svn-id: svn://svn.chromium.org/blink/trunk@175141 bbb929c8-8fbe-4397-9dbb-9b2b20218538