Make getKeys, getValues getters (keys, values).

lib/core/expect.dart

Index: lib/core/expect.dart
diff --git a/lib/core/expect.dart b/lib/core/expect.dart
index bdd24eb1f29ef28588d43bc4caff3f72b131a821..adf0604666f3101ab70c40f497ce1671d2d7be1d 100644
--- a/lib/core/expect.dart
+++ b/lib/core/expect.dart
@@ -131,7 +131,7 @@ class Expect {
     String msg = _getMessage(reason);
 
     // Make sure all of the values are present in both and match.
-    for (final key in expected.getKeys()) {
+    for (final key in expected.keys) {
       if (!actual.containsKey(key)) {
         _fail('Expect.mapEquals(missing expected key: <$key>$msg) fails');
       }
@@ -140,7 +140,7 @@ class Expect {
     }
 
     // Make sure the actual map doesn't have any extra keys.
-    for (final key in actual.getKeys()) {
+    for (final key in actual.keys) {
       if (!expected.containsKey(key)) {
         _fail('Expect.mapEquals(unexpected key: <$key>$msg) fails');
       }