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

extensions/shell/browser/default_shell_browser_main_delegate.cc

Index: extensions/shell/browser/default_shell_browser_main_delegate.cc
diff --git a/extensions/shell/browser/default_shell_browser_main_delegate.cc b/extensions/shell/browser/default_shell_browser_main_delegate.cc
index 877926b21026478b4094ea3d1eba033140f4e787..978d27378d9f0887786651fe96676732ca7f2076 100644
--- a/extensions/shell/browser/default_shell_browser_main_delegate.cc
+++ b/extensions/shell/browser/default_shell_browser_main_delegate.cc
@@ -9,9 +9,12 @@
 #include "base/files/file_util.h"
 #include "base/strings/string_tokenizer.h"
 #include "extensions/common/switches.h"
-#include "extensions/shell/browser/shell_desktop_controller.h"
 #include "extensions/shell/browser/shell_extension_system.h"
 
+#if defined(USE_AURA)
+#include "extensions/shell/browser/shell_desktop_controller_aura.h"
+#endif
+
 namespace extensions {
 
 DefaultShellBrowserMainDelegate::DefaultShellBrowserMainDelegate() {
@@ -62,7 +65,11 @@ void DefaultShellBrowserMainDelegate::Shutdown() {
 }
 
 DesktopController* DefaultShellBrowserMainDelegate::CreateDesktopController() {
-  return new ShellDesktopController();
+#if defined(USE_AURA)
+  return new ShellDesktopControllerAura();
+#else
+  return NULL;
+#endif
 }
 
 }  // namespace extensions