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 7e49f52e41184bbcac078f9b3e1dbd31dcc29688..0e17df2b73e13c66ec8fc862706b9695c4ece97d 100644
--- a/extensions/shell/browser/default_shell_browser_main_delegate.cc
+++ b/extensions/shell/browser/default_shell_browser_main_delegate.cc
@@ -8,10 +8,13 @@
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/strings/string_tokenizer.h"
-#include "extensions/shell/browser/shell_desktop_controller.h"
 #include "extensions/shell/browser/shell_extension_system.h"
 #include "extensions/shell/common/switches.h"
 
+#if defined(USE_AURA)
+#include "extensions/shell/browser/shell_desktop_controller_aura.h"
+#endif
+
 namespace extensions {
 
 DefaultShellBrowserMainDelegate::DefaultShellBrowserMainDelegate() {
@@ -53,7 +56,11 @@ void DefaultShellBrowserMainDelegate::Shutdown() {
 }
 
 DesktopController* DefaultShellBrowserMainDelegate::CreateDesktopController() {
-  return new ShellDesktopController();
+#if defined(USE_AURA)
+  return new ShellDesktopControllerAura();
+#else
+  return NULL;
+#endif
 }
 
 }  // namespace extensions