mus: Add PointerWatcher for passively observing mouse and touch events

ash/test/test_shell_delegate.h

Index: ash/test/test_shell_delegate.h
diff --git a/ash/test/test_shell_delegate.h b/ash/test/test_shell_delegate.h
index 2c3a6333c00e2fa7584a6dbbcdf5eeea96864dfe..f2296962197618e07fa39ee71afb7598c0624f20 100644
--- a/ash/test/test_shell_delegate.h
+++ b/ash/test/test_shell_delegate.h
@@ -61,6 +61,8 @@ class TestShellDelegate : public ShellDelegate {
   AccessibilityDelegate* CreateAccessibilityDelegate() override;
   NewWindowDelegate* CreateNewWindowDelegate() override;
   MediaDelegate* CreateMediaDelegate() override;
+  std::unique_ptr<PointerWatcherDelegate> CreatePointerWatcherDelegate()
+      override;
   ui::MenuModel* CreateContextMenu(ash::Shelf* shelf,
                                    const ash::ShelfItem* item) override;
   GPUSupport* CreateGPUSupport() override;