fix spelling in core libraries

sdk/lib/_internal/js_runtime/lib/constant_map.dart

Index: sdk/lib/_internal/js_runtime/lib/constant_map.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/constant_map.dart b/sdk/lib/_internal/js_runtime/lib/constant_map.dart
index 9e98b13dd3fbaa7e6d7509d0dd8dfff7037cab59..693197b146da0b5eba108c1f871554f9ae8547dd 100644
--- a/sdk/lib/_internal/js_runtime/lib/constant_map.dart
+++ b/sdk/lib/_internal/js_runtime/lib/constant_map.dart
@@ -98,8 +98,8 @@ class ConstantStringMap<K, V> extends ConstantMap<K, V> {
   _fetch(key) => jsPropertyAccess(_jsObject, key);
 
   void forEach(void f(K key, V value)) {
-    // Use a JS 'cast' to get efficient loop.  Type inferrence doesn't get this
-    // since constant map representation is chosen after type inferrence and the
+    // Use a JS 'cast' to get efficient loop.  Type inference doesn't get this
+    // since constant map representation is chosen after type inference and the
     // instantiation is shortcut by the compiler.
     var keys = _keysArray;
     for (int i = 0; i < keys.length; i++) {