DevTools: Overriding the String global object and opening the debugger crashes the browser tab and stops the debugger

BUG=305199

Review URL: https://codereview.chromium.org/26640005

git-svn-id: svn://svn.chromium.org/blink/trunk@159259 bbb929c8-8fbe-4397-9dbb-9b2b20218538