re-re-land of https://codereview.chromium.org/11364053/

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 b3706dbca522f12a6c6742cc2e3fc9377af654b2..e406d765b23289ce7f773599653c411a95849824 100644
--- a/ash/test/test_shell_delegate.cc
+++ b/ash/test/test_shell_delegate.cc
@@ -10,6 +10,7 @@
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/test/test_launcher_delegate.h"
+#include "ash/wm/stacking_controller.h"
 #include "ash/wm/window_util.h"
 #include "content/public/test/test_browser_context.h"
 #include "ui/aura/window.h"
@@ -161,6 +162,10 @@ double TestShellDelegate::GetSavedScreenMagnifierScale() {
   return std::numeric_limits<double>::min();
 }
 
+aura::client::StackingClient* TestShellDelegate::CreateStackingClient() {
+  return new StackingController;
+}
+
 void TestShellDelegate::SetSessionStarted(bool session_started) {
   session_started_ = session_started;
   if (session_started)