[Flutter][Scenic] Add ViewHolderConnected event to platform_view

Fidl event added in fxr/263828.

Tested: -astro
Change-Id: I779cedf216bce0afb0b161a50516facbba90c8e6
diff --git a/runtime/flutter_runner/platform_view.cc b/runtime/flutter_runner/platform_view.cc
index 4025dc1..bc46ba9 100644
--- a/runtime/flutter_runner/platform_view.cc
+++ b/runtime/flutter_runner/platform_view.cc
@@ -393,6 +393,11 @@
                 << "Flutter PlatformView::OnScenicEvent: Unhandled GFX event "
                    "(fuchsia.ui.gfx.ViewDisconnectedEvent).";
             break;
+          case fuchsia::ui::gfx::Event::Tag::kViewHolderConnected:
+            FML_LOG(WARNING)
+                << "Flutter PlatformView::OnScenicEvent: Unhandled GFX event "
+                   "(fuchsia.ui.gfx.kViewHolderConnected).";
+            break;
           case fuchsia::ui::gfx::Event::Tag::kViewHolderDisconnected:
             FML_LOG(WARNING)
                 << "Flutter PlatformView::OnScenicEvent: Unhandled GFX event "