chromeos: changes how DisplayManagerObservers are notified

ui/aura/test/mus/test_window_manager_client.cc

Index: ui/aura/test/mus/test_window_manager_client.cc
diff --git a/ui/aura/test/mus/test_window_manager_client.cc b/ui/aura/test/mus/test_window_manager_client.cc
index 11154fb7791919446794c8455bf7c584a84dc4d2..0131e122978eea12518340c3c1d5c5e146332b59 100644
--- a/ui/aura/test/mus/test_window_manager_client.cc
+++ b/ui/aura/test/mus/test_window_manager_client.cc
@@ -44,6 +44,12 @@ void TestWindowManagerClient::SetDisplayRoot(
     Id window_id,
     const SetDisplayRootCallback& callback) {}
 
+void TestWindowManagerClient::SetDisplayConfiguration(
+    const std::vector<display::Display>& displays,
+    std::vector<::ui::mojom::WmViewportMetricsPtr> viewport_metrics,
+    int64_t primary_display_id,
+    const SetDisplayConfigurationCallback& callback) {}
+
 void TestWindowManagerClient::WmResponse(uint32_t change_id, bool response) {}
 
 void TestWindowManagerClient::WmSetBoundsResponse(uint32_t change_id) {}