Fix crash in isDocumentDoneLoading()

Document::loader() might be null if re-entrancy is involved.

BUG=357570

Review URL: https://codereview.chromium.org/222433003

git-svn-id: svn://svn.chromium.org/blink/trunk@170693 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove dead code from RenderBox:sizesLogicalWidthToFitContent()

Review URL: https://codereview.chromium.org/219333009

git-svn-id: svn://svn.chromium.org/blink/trunk@170695 bbb929c8-8fbe-4397-9dbb-9b2b20218538