Capture and handle properly every call to JSArray that read or writes elements via a native call

tests/compiler/dart2js/mock_compiler.dart

Index: tests/compiler/dart2js/mock_compiler.dart
diff --git a/tests/compiler/dart2js/mock_compiler.dart b/tests/compiler/dart2js/mock_compiler.dart
index 351080146b8af5b6e30c88ab4010383c53b3dee2..009bbe8bbc39022edb4a8a86b428a711c80caced 100644
--- a/tests/compiler/dart2js/mock_compiler.dart
+++ b/tests/compiler/dart2js/mock_compiler.dart
@@ -107,7 +107,10 @@ const String DEFAULT_INTERCEPTORSLIB = r'''
     var length;
     operator[](index) => this[index];
     operator[]=(index, value) {}
-    var add;
+    add(value) {}
+    removeAt(index) {}
+    insert(index, value) {}
+    removeLast() {}
   }
   class JSMutableArray extends JSArray implements JSMutableIndexable {}
   class JSFixedArray extends JSMutableArray {}