Refactor ShellDesktopController and ShellNativeAppWindow to allow for non-aura implementations.

athena/main/athena_main_delegate.cc

Index: athena/main/athena_main_delegate.cc
diff --git a/athena/main/athena_main_delegate.cc b/athena/main/athena_main_delegate.cc
index 59c6c42dbda39d2ffc2866dee427a1aa811ac39d..1d70272aba838d84c9bee585c49a476e125f1b54 100644
--- a/athena/main/athena_main_delegate.cc
+++ b/athena/main/athena_main_delegate.cc
@@ -23,7 +23,10 @@
 #include "extensions/shell/common/switches.h"
 #include "extensions/shell/renderer/shell_content_renderer_client.h"
 #include "ppapi/c/private/ppb_pdf.h"
+#include "ui/aura/window.h"
+#include "ui/aura/window_tree_host.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/geometry/size.h"
 
 namespace athena {
 namespace {
@@ -40,8 +43,8 @@ class AthenaDesktopController : public extensions::DesktopController {
 
  private:
   // extensions::DesktopController:
-  virtual aura::WindowTreeHost* GetHost() override {
-    return athena::AthenaEnv::Get()->GetHost();
+  virtual gfx::Size GetWindowSize() override {
+    return athena::AthenaEnv::Get()->GetHost()->window()->bounds().size();
   }
 
   // Creates a new app window and adds it to the desktop. The desktop maintains