Version 2.11.0-213.5.beta

* Cherry-pick 34b485c to beta

Author: athomas

sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/classes.dart

@@ -435,6 +435,13 @@ void _applyExtension(jsType, dartExtType) {
     return;
   }
 
+  if (JS('!', '# === #.Object', jsType, global_)) {
+    var extName = JS<String>('!', '#.name', dartExtType);
+    _warn(
+        "Attempting to install properties from non-Object type '$extName' onto the native JS Object.");
+    return;
+  }
+
   _installProperties(
       jsProto, dartExtType, JS('', '#[#]', jsProto, _extensionType));
 

tools/VERSION

@@ -28,4 +28,4 @@ MAJOR 2
 MINOR 11
 PATCH 0
 PRERELEASE 213
-PRERELEASE_PATCH 4
+PRERELEASE_PATCH 5