extensions: Cleanup class/struct fwd declarations

extensions/shell/browser/desktop_controller.h

Index: extensions/shell/browser/desktop_controller.h
diff --git a/extensions/shell/browser/desktop_controller.h b/extensions/shell/browser/desktop_controller.h
index bdcd8e1b7743e81b4e977fedf463affe1bcbafee..72247772a3c46d33823d881f74b8b62fda665695 100644
--- a/extensions/shell/browser/desktop_controller.h
+++ b/extensions/shell/browser/desktop_controller.h
@@ -7,11 +7,6 @@
 
 #include "ui/gfx/native_widget_types.h"
 
-namespace aura {
-class Window;
-class WindowTreeHost;
-}
-
 namespace content {
 class BrowserContext;
 }
@@ -23,7 +18,6 @@ class Size;
 namespace extensions {
 class AppWindow;
 class Extension;
-class ShellAppWindow;
 
 // DesktopController is an interface to construct the window environment in
 // extensions shell. ShellDesktopControllerAura provides a default