Revert 236040 "Support headless content_shell for linux/aura."

This broke fast/dom/Window/open-window-min-size.html on windows (at least on XP, maybe other windows also)

> Support headless content_shell for linux/aura.
> 
> When running blink layout tests, we shouldn't create native windows. We should
> rather just create the virtual content window for render of content. Headless
> mode of content shell support is already present on other ports and needs to be
> added for aura. It is important in terms of performance (when running layout tests).
> 
> BUG=316712
> 
> R=jochen
> 
> TEST=None; no behavior change;
> 
> Review URL: https://codereview.chromium.org/71243002

TBR=r.kasibhatla@samsung.com

Review URL: https://codereview.chromium.org/70093006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236065 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236065