V2 app support step2 : Use NativeAppWindow for Activity's window.

athena/content/app_activity.h

Index: athena/content/app_activity.h
diff --git a/athena/content/app_activity.h b/athena/content/app_activity.h
index 3c6959668ea3536d3ecf299ada2ab1ded7a68a99..c721446480fe31d0ef3cffd9241111c88fc040fc 100644
--- a/athena/content/app_activity.h
+++ b/athena/content/app_activity.h
@@ -10,10 +10,6 @@
 #include "content/public/browser/web_contents_observer.h"
 #include "ui/gfx/image/image_skia.h"
 
-namespace contents {
-class WebContents;
-}
-
 namespace views {
 class WebView;
 }
@@ -57,7 +53,7 @@ class AppActivity : public Activity,
   virtual void DidUpdateFaviconURL(
       const std::vector<content::FaviconURL>& candidates) OVERRIDE;
 
-  virtual content::WebContents* GetWebContents() = 0;
+  virtual views::WebView* GetWebView() = 0;
 
  private:
   // Register this activity with its application.