Moves NewWindowDelegate to ash/common

ash/mus/shell_delegate_mus.cc

Index: ash/mus/shell_delegate_mus.cc
diff --git a/ash/mus/shell_delegate_mus.cc b/ash/mus/shell_delegate_mus.cc
index 301f6157a9a78b4cfc03709555c0b81bdde954ad..15c61802d1e1cb5d53d8c78d36a0381b633d095f 100644
--- a/ash/mus/shell_delegate_mus.cc
+++ b/ash/mus/shell_delegate_mus.cc
@@ -12,6 +12,7 @@
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/system/tray/default_system_tray_delegate.h"
 #include "ash/mus/accessibility_delegate_mus.h"
+#include "ash/mus/new_window_delegate_mus.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string16.h"
 #include "components/user_manager/user_info_impl.h"
@@ -187,8 +188,7 @@ AccessibilityDelegate* ShellDelegateMus::CreateAccessibilityDelegate() {
 }
 
 NewWindowDelegate* ShellDelegateMus::CreateNewWindowDelegate() {
-  NOTIMPLEMENTED();
-  return nullptr;
+  return new mus::NewWindowDelegateMus;
 }
 
 MediaDelegate* ShellDelegateMus::CreateMediaDelegate() {