Minimize headless code that refers to aura.

headless/lib/browser/headless_browser_context_impl.cc

Index: headless/lib/browser/headless_browser_context_impl.cc
diff --git a/headless/lib/browser/headless_browser_context_impl.cc b/headless/lib/browser/headless_browser_context_impl.cc
index df65523f34b7055eb8479088f2b477960588aad7..0d4de19955513415dd7baa1fc63af70f30158157 100644
--- a/headless/lib/browser/headless_browser_context_impl.cc
+++ b/headless/lib/browser/headless_browser_context_impl.cc
@@ -21,7 +21,6 @@
 #include "headless/public/util/black_hole_protocol_handler.h"
 #include "headless/public/util/in_memory_protocol_handler.h"
 #include "net/url_request/url_request_context.h"
-#include "ui/aura/window_tree_host.h"
 
 namespace headless {
 
@@ -249,8 +248,7 @@ HeadlessWebContents* HeadlessBrowserContextImpl::CreateWebContents(
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   std::unique_ptr<HeadlessWebContentsImpl> headless_web_contents =
-      HeadlessWebContentsImpl::Create(builder,
-                                      browser()->window_tree_host()->window());
+      HeadlessWebContentsImpl::Create(builder);
 
   if (!headless_web_contents) {
     return nullptr;