ash: Add RootWindowHostFactory class.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index ba58f5dbf4cface476077125d719b02221ac9b2d..9e7b67ac066f433a55d5490278d728dc5c7646c9 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -23,6 +23,7 @@
 #include "ash/magnifier/magnification_controller.h"
 #include "ash/magnifier/partial_magnification_controller.h"
 #include "ash/root_window_controller.h"
+#include "ash/root_window_delegate.h"
 #include "ash/screen_ash.h"
 #include "ash/shell_delegate.h"
 #include "ash/shell_factory.h"
@@ -200,7 +201,7 @@ Shell::Shell(ShellDelegate* delegate)
       browser_context_(NULL),
       simulate_modal_window_open_for_testing_(false) {
   DCHECK(delegate_.get());
-  display_manager_.reset(new internal::DisplayManager);
+  display_manager_.reset(new internal::DisplayManager(this));
   ANNOTATE_LEAKING_OBJECT_PTR(screen_);  // see crbug.com/156466
   gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_ALTERNATE, screen_);
   if (!gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_NATIVE))
@@ -880,4 +881,11 @@ void Shell::OnEvent(ui::Event* event) {
   }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Shell, ash::internal::DisplayManagerDelegate overrides:
+
+aura::RootWindowDelegate* Shell::CreateRootWindowDelegate() {
+  return delegate_->CreateRootWindowDelegate();
+}
+
 }  // namespace ash