Do not attempt to apply app sync updates to extensions with matching ID, or vice versa.

chrome/browser/extensions/extension_service.cc

Index: chrome/browser/extensions/extension_service.cc
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index 2f1874f40832b29c697f7e00e569cbc35d81c02c..8712e6fc5d42235a7596a81d681b34aa15bcacb2 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -1638,6 +1638,17 @@ void ExtensionService::ProcessSyncData(
     ExtensionFilter filter) {
   const std::string& id = extension_sync_data.id;
 
+  // If we have an app update for an extension, or vice versa, ignore it.
+  //
+  // This can happen if an app author publishes an update that is actually an
+  // extension, for example.
+  const Extension* extension_if_installed =
+      GetExtensionByIdInternal(id, true, true, true);
+  if (extension_if_installed && !filter(*extension_if_installed)) {
+    LOG(WARNING) << "Attempt to sync wrong type of extension for " << id;
+    return;
+  }
+
   // Handle uninstalls first.
   if (extension_sync_data.uninstalled) {
     std::string error;