Revert 172006 "Make window's navigator / history properties non ..."

Speculative revert. I suspect this broke browser_tests
PlatformAppBrowserTest.Restrictions.

> Make window's navigator / history properties non replaceable
> 
> Make window's navigator / history properties non replaceable to match
> the specification:
> http://www.whatwg.org/specs/web-apps/current-work/multipage/browsers.html#window
> 
> The new behavior also matches the behavior of Firefox 28 and IE11.
> 
> R=arv@chromium.org, tkent@chromium.org
> BUG=364512
> TEST=fast/dom/Window/get-set-properties.html
> 
> Review URL: https://codereview.chromium.org/243203002

TBR=ch.dumez@samsung.com
BUG=364512

Review URL: https://codereview.chromium.org/244763002

git-svn-id: svn://svn.chromium.org/blink/trunk@172014 bbb929c8-8fbe-4397-9dbb-9b2b20218538