mash: Replace int ShelfIDs with AppLaunchID strings.

ash/public/cpp/mus_property_mirror_ash.cc

Index: ash/public/cpp/mus_property_mirror_ash.cc
diff --git a/ash/public/cpp/mus_property_mirror_ash.cc b/ash/public/cpp/mus_property_mirror_ash.cc
index 770c4a1ff6fc1540ccba1a2f4392daee835939df..a9b634eeffbf3aa47c7eb46dbabc97adf9d840e9 100644
--- a/ash/public/cpp/mus_property_mirror_ash.cc
+++ b/ash/public/cpp/mus_property_mirror_ash.cc
@@ -42,8 +42,8 @@ void MusPropertyMirrorAsh::MirrorPropertyFromWidgetWindowToRootWindow(
     root_window->SetProperty(kWindowPinTypeKey, value);
   } else if (key == aura::client::kAppIconKey) {
     MirrorOwnedProperty(window, root_window, aura::client::kAppIconKey);
-  } else if (key == aura::client::kAppIdKey) {
-    MirrorOwnedProperty(window, root_window, aura::client::kAppIdKey);
+  } else if (key == kShelfIDKey) {
+    MirrorOwnedProperty(window, root_window, kShelfIDKey);
   } else if (key == aura::client::kDrawAttentionKey) {
     bool value = window->GetProperty(aura::client::kDrawAttentionKey);
     root_window->SetProperty(aura::client::kDrawAttentionKey, value);