Check for null prototype in isJavaScriptSimpleObject

sdk/lib/html/html_common/conversions.dart

Index: sdk/lib/html/html_common/conversions.dart
diff --git a/sdk/lib/html/html_common/conversions.dart b/sdk/lib/html/html_common/conversions.dart
index 255b3e5e65140d4161f0a1d88d24d0f22148e214..042a78472455fa7443a8830e423e4302d21631ec 100644
--- a/sdk/lib/html/html_common/conversions.dart
+++ b/sdk/lib/html/html_common/conversions.dart
@@ -392,8 +392,11 @@ convertDartToNative_ImageData(ImageData imageData) {
 bool isJavaScriptDate(value) => JS('bool', '# instanceof Date', value);
 bool isJavaScriptRegExp(value) => JS('bool', '# instanceof RegExp', value);
 bool isJavaScriptArray(value) => JS('bool', '# instanceof Array', value);
-bool isJavaScriptSimpleObject(value) =>
-    JS('bool', 'Object.getPrototypeOf(#) === Object.prototype', value);
+bool isJavaScriptSimpleObject(value) {
+  var proto = JS('', 'Object.getPrototypeOf(#)', value);
+  return JS('bool', '# === Object.prototype', proto) ||
+      JS('bool', '# === null', proto);
+}
 bool isImmutableJavaScriptArray(value) =>
     JS('bool', r'!!(#.immutable$list)', value);