NoOp Document::open shouldn't be reported to Inspector.

Otherwise Inspector erroneously thinks that frame was navigated.

BUG=315618

Review URL: https://codereview.chromium.org/61643008

git-svn-id: svn://svn.chromium.org/blink/trunk@162344 bbb929c8-8fbe-4397-9dbb-9b2b20218538