DevTools: Console object preview should not be lossless if it has accessors.

After expanding an accessor in the preview, the value may not be lossless
(e.g. a long truncated string), thus assume such preview not lossless as well.

BUG=261470
R=pfeldman

Review URL: https://codereview.chromium.org/137883002

git-svn-id: svn://svn.chromium.org/blink/trunk@165046 bbb929c8-8fbe-4397-9dbb-9b2b20218538