Minimize headless code that refers to aura.

headless/lib/browser/headless_browser_impl.cc

Index: headless/lib/browser/headless_browser_impl.cc
diff --git a/headless/lib/browser/headless_browser_impl.cc b/headless/lib/browser/headless_browser_impl.cc
index 93d6918a76c8d022a1f46f57296f2c8f5da45f1a..5e950d807da81f58b595da523e985ddb9d62dae7 100644
--- a/headless/lib/browser/headless_browser_impl.cc
+++ b/headless/lib/browser/headless_browser_impl.cc
@@ -18,8 +18,6 @@
 #include "headless/lib/browser/headless_browser_context_impl.h"
 #include "headless/lib/browser/headless_browser_main_parts.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
-#include "headless/lib/browser/headless_window_parenting_client.h"
-#include "headless/lib/browser/headless_window_tree_host.h"
 #include "headless/lib/headless_content_main_delegate.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
@@ -121,17 +119,7 @@ void HeadlessBrowserImpl::set_browser_main_parts(
 }
 
 void HeadlessBrowserImpl::RunOnStartCallback() {
-  DCHECK(aura::Env::GetInstance());
-  ui::DeviceDataManager::CreateInstance();
-
-  window_tree_host_.reset(
-      new HeadlessWindowTreeHost(gfx::Rect(options()->window_size)));
-  window_tree_host_->InitHost();
-  window_tree_host_->window()->Show();
-
-  window_parenting_client_.reset(
-      new HeadlessWindowParentingClient(window_tree_host_->window()));
-
+  PlatformCreateWindow();
   on_start_callback_.Run(this);
   on_start_callback_ = base::Callback<void(HeadlessBrowser*)>();
 }
@@ -179,10 +167,6 @@ base::WeakPtr<HeadlessBrowserImpl> HeadlessBrowserImpl::GetWeakPtr() {
   return weak_ptr_factory_.GetWeakPtr();
 }
 
-aura::WindowTreeHost* HeadlessBrowserImpl::window_tree_host() const {
-  return window_tree_host_.get();
-}
-
 HeadlessWebContents* HeadlessBrowserImpl::GetWebContentsForDevToolsAgentHostId(
     const std::string& devtools_agent_host_id) {
   for (HeadlessBrowserContext* context : GetAllBrowserContexts()) {