Minimize headless code that refers to aura.

headless/lib/browser/headless_browser_impl.h

Index: headless/lib/browser/headless_browser_impl.h
diff --git a/headless/lib/browser/headless_browser_impl.h b/headless/lib/browser/headless_browser_impl.h
index f37dff1dbc45b8c135fde8db85f6f33f53ff0160..eb5af5eb4c11eb466ceccb39be336f712ad270dd 100644
--- a/headless/lib/browser/headless_browser_impl.h
+++ b/headless/lib/browser/headless_browser_impl.h
@@ -13,16 +13,13 @@
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
+#include "content/public/browser/web_contents.h"
 #include "headless/lib/browser/headless_devtools_manager_delegate.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
 
-namespace aura {
-class WindowTreeHost;
-
-namespace client {
-class WindowParentingClient;
-}
-}
+#if defined(USE_AURA)
+#include "headless/lib/browser/headless_window_tree_host.h"
+#endif
 
 namespace headless {
 
@@ -70,18 +67,24 @@ class HeadlessBrowserImpl : public HeadlessBrowser {
 
   base::WeakPtr<HeadlessBrowserImpl> GetWeakPtr();
 
-  aura::WindowTreeHost* window_tree_host() const;
+  // All the methods that begin with Platform need to be implemented by the
+  // platform specific headless implementation.
+  // Helper for one time initialization of application
+  void PlatformInitialize();
+  void PlatformCreateWindow();
+  void PlatformSetWebContents(const gfx::Size& initial_size,
+                              content::WebContents* web_contents);
 
  protected:
-  base::Callback<void(HeadlessBrowser*)> on_start_callback_;
-  HeadlessBrowser::Options options_;
-  HeadlessBrowserMainParts* browser_main_parts_;  // Not owned.
-
+#if defined(USE_AURA)
   // TODO(eseckler): Currently one window and one window_tree_host
   // is used for all web contents. We should probably use one
   // window per web contents, but additional investigation is needed.
-  std::unique_ptr<aura::WindowTreeHost> window_tree_host_;
-  std::unique_ptr<aura::client::WindowParentingClient> window_parenting_client_;
+  std::unique_ptr<HeadlessWindowTreeHost> window_tree_host_;
+#endif
+  base::Callback<void(HeadlessBrowser*)> on_start_callback_;
+  HeadlessBrowser::Options options_;
+  HeadlessBrowserMainParts* browser_main_parts_;  // Not owned.
 
   std::unordered_map<std::string, std::unique_ptr<HeadlessBrowserContextImpl>>
       browser_contexts_;