Support abstract getters without parameters.

dart/lib/compiler/implementation/tree/dartstring.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * The [DartString] type represents a Dart string value as a sequence of Unicode
  * Scalar Values.
  * After parsing, any valid [LiteralString] will contain a [DartString]
  * representing its content after removing quotes and resolving escapes in
  * its source.
  */
 class DartString implements Iterable<int> {
   factory DartString.empty() => const LiteralDartString("");
   // This is a convenience constructor. If you need a const literal DartString,
   // use [const LiteralDartString(string)] directly.
   factory DartString.literal(String string) => new LiteralDartString(string);
   factory DartString.rawString(SourceString source, int length) =>
       new RawSourceDartString(source, length);
   factory DartString.escapedString(SourceString source, int length) =>
       new EscapedSourceDartString(source, length);
   factory DartString.concat(DartString first, DartString second) {
     if (first.isEmpty()) return second;
     if (second.isEmpty()) return first;
     return new ConsDartString(first, second);
   }
   const DartString();
-  abstract int get length();
+  abstract int get length;
   bool isEmpty() => length == 0;
   abstract Iterator<int> iterator();
   abstract String slowToString();
 
   bool operator ==(var other) {
     if (other is !DartString) return false;
     DartString otherString = other;
     if (length != otherString.length) return false;
     Iterator it1 = iterator();
     Iterator it2 = otherString.iterator();
     while (it1.hasNext()) {
       if (it1.next() != it2.next()) return false;
     }
     return true;
   }
   String toString() => "DartString#${length}:${slowToString()}";
-  abstract SourceString get source();
+  abstract SourceString get source;
 }
 
 
 /**
  * A [DartString] where the content is represented by an actual [String].
  */
 class LiteralDartString extends DartString {
   final String string;
   const LiteralDartString(this.string);
   int get length => string.length;
@@ skipping 145 matching lines @@
       for (int i = 0; i < 3; i++) {
         code = source.next();
         value = value * 16 + hexDigitValue(code);
       }
       return value;
     }
     return code;
   }
 }