Revert 172134 "Make window.screen property non replaceable"

This caused timeouts of Chrome OS browser_tests
TermsOfServiceTestInstance/TermsOfServiceTest.TermsOfServiceScreen/0
and /1.

> Make window.screen property non replaceable
> 
> Make window.screen property non replaceable for consistency with other
> browsers (tested with Firefox 28 and IE11).
> 
> This CL also adds an internals.setOverrideScreenData() utility function for
> Layout tests as the fast/forms/page-popup/page-popup-adjust-rect.html test
> needs to be able to override the screen object.
> 
> BUG=364937
> TEST=fast/dom/Window/get-set-properties.html
> 
> Review URL: https://codereview.chromium.org/243173004

TBR=ch.dumez@samsung.com

Review URL: https://codereview.chromium.org/248643002

git-svn-id: svn://svn.chromium.org/blink/trunk@172311 bbb929c8-8fbe-4397-9dbb-9b2b20218538