ash: Add RootWindowHostFactory class.

ash/test/test_shell_delegate.cc

Index: ash/test/test_shell_delegate.cc
diff --git a/ash/test/test_shell_delegate.cc b/ash/test/test_shell_delegate.cc
index 066a14bd540c22005f63606c79a0d2bde4b4d34b..30967afe0b5800ba75d9060a321b22548b14efb8 100644
--- a/ash/test/test_shell_delegate.cc
+++ b/ash/test/test_shell_delegate.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "ash/caps_lock_delegate_stub.h"
+#include "ash/host/root_window_host_factory.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/test/test_launcher_delegate.h"
@@ -202,6 +203,10 @@ bool TestShellDelegate::IsSearchKeyActingAsFunctionKey() const {
   return is_search_key_acting_as_function_key_;
 }
 
+RootWindowHostFactory* TestShellDelegate::CreateRootWindowHostFactory() {
+  return RootWindowHostFactory::Create();
+}
+
 void TestShellDelegate::SetSessionStarted(bool session_started) {
   session_started_ = session_started;
   if (session_started)