a === b -> identical(a, b)

runtime/lib/growable_array.dart

Index: runtime/lib/growable_array.dart
diff --git a/runtime/lib/growable_array.dart b/runtime/lib/growable_array.dart
index a8462a37d0ef02d39b10469c83fe0b36ce7b8fa9..d02cccca0bc8bfb6014aeb7b10c8f0ddc0ddf14e 100644
--- a/runtime/lib/growable_array.dart
+++ b/runtime/lib/growable_array.dart
@@ -154,7 +154,7 @@ class _GrowableObjectArray<T> implements List<T> {
   }
 
   int lastIndexOf(T element, [int start = null]) {
-    if (start === null) start = length - 1;
+    if (start == null) start = length - 1;
     return Arrays.lastIndexOf(this, element, start);
   }
 
@@ -200,7 +200,7 @@ class _GrowableObjectArray<T> implements List<T> {
   }
 
   bool get isEmpty {
-    return this.length === 0;
+    return this.length == 0;
   }
 
   void clear() {