DevTools: restore command line API functionality while on a breakpoint.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=156787

Review URL: https://chromiumcodereview.appspot.com/23495003

git-svn-id: svn://svn.chromium.org/blink/trunk@156837 bbb929c8-8fbe-4397-9dbb-9b2b20218538