Get rid of a lot of () for getters.

lib/coreimpl/hash_map_set.dart

Index: lib/coreimpl/hash_map_set.dart
diff --git a/lib/coreimpl/hash_map_set.dart b/lib/coreimpl/hash_map_set.dart
index 37c1cfb6ad71572b064779e5d597ea356b232826..8d5ee2cabb06e4379cfe87b46002f2662b84e697 100644
--- a/lib/coreimpl/hash_map_set.dart
+++ b/lib/coreimpl/hash_map_set.dart
@@ -221,7 +221,7 @@ class HashMapImplementation<K extends Hashable, V> implements HashMap<K, V> {
     return _numberOfEntries == 0;
   }
 
-  int get length() {
+  int get length {
     return _numberOfEntries;
   }
 
@@ -377,7 +377,7 @@ class HashSetImplementation<E extends Hashable> implements HashSet<E> {
     return _backingMap.isEmpty();
   }
 
-  int get length() {
+  int get length {
     return _backingMap.length;
   }