Revert 229521 "Revert 229507 "aura: Allow creating content_shell..."

Revert didn't help, so reland the change.

> Revert 229507 "aura: Allow creating content_shell without views."
> 
> Speculative. All windows bots on the main waterfall except for the clobber
> builder started timing out during compile during a window that had only this
> change and two test-only changes in the range.
> 
> > aura: Allow creating content_shell without views.
> > 
> > This builds content_shell with use_aura=1 and toolkit_views=0.
> > 
> > BUG=none
> > R=derat@chromium.org, jamescook@chromium.org, jochen@chromium.org
> > 
> > Review URL: https://codereview.chromium.org/26695007
> 
> TBR=sadrul@chromium.org
> 
> Review URL: https://codereview.chromium.org/30413002

TBR=thakis@chromium.org

Review URL: https://codereview.chromium.org/27993005

git-svn-id: http://src.chromium.org/svn/trunk/src/build@229524 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

build_config.h

@@ -31,7 +31,7 @@
 #elif defined(__linux__)
 #define OS_LINUX 1
 // Use TOOLKIT_GTK on linux if TOOLKIT_VIEWS isn't defined.
-#if !defined(TOOLKIT_VIEWS) && defined(USE_X11)
+#if !defined(TOOLKIT_VIEWS) && defined(USE_X11) && !defined(USE_AURA)
 #define TOOLKIT_GTK
 #endif
 #if defined(__GLIBC__) && !defined(__UCLIBC__)