DevTools: Prevent a debugger pause while executing js code in releaseObjectGroup

V8 part of change: https://codereview.chromium.org/473913002

BUG=

Review URL: https://codereview.chromium.org/473923002

git-svn-id: svn://svn.chromium.org/blink/trunk@180847 bbb929c8-8fbe-4397-9dbb-9b2b20218538