dart2js: Use frequency of occurence to sort metadata indices.

pkg/compiler/lib/src/constants/expressions.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.constants.expressions;
 
 import '../constants/constant_system.dart';
 import '../dart2jslib.dart' show assertDebugMode, Compiler;
 import '../dart_types.dart';
 import '../elements/elements.dart' show
@@ skipping 10 matching lines @@
 
 enum ConstantExpressionKind {
   BINARY,
   BOOL,
   BOOL_FROM_ENVIRONMENT,
   CONCATENATE,
   CONDITIONAL,
   CONSTRUCTED,
   DEFERRED,
   DOUBLE,
+  DUMMY,
   ERRONEOUS,
   FUNCTION,
   IDENTICAL,
   INT,
   INT_FROM_ENVIRONMENT,
   LIST,
   MAP,
   NULL,
   STRING,
   STRING_FROM_ENVIRONMENT,
@@ skipping 287 matching lines @@
     return value;
   }
 
   @override
   int _computeHashCode() => 13;
 
   @override
   bool _equals(ErroneousConstantExpression other) => true;
 }
 
+class DummyConstantExpression extends ConstantExpression {

[Johnni Winther, 2015/05/28 12:07:17]

Add a TODO for me to see if we can avoid the need for this.

[herhut, 2015/06/01 12:09:41]

Done.

+  final DummyConstantValue value;
+
+  DummyConstantExpression(this.value);
+
+  @override
+  ConstantValue evaluate(Environment environment,
+                         ConstantSystem constantSystem) {
+    return value;
+  }
+
+  @override
+  int _computeHashCode() => 13 * value.hashCode;
+
+  accept(ConstantExpressionVisitor visitor, [context]) {
+    throw "unsupported";
+  }
+
+  @override
+  bool _equals(BoolConstantExpression other) {
+    return value == other.value;
+  }
+
+  ConstantExpressionKind get kind => ConstantExpressionKind.DUMMY;
+}
+
+
+
 /// A boolean, int, double, string, or null constant.
 abstract class PrimitiveConstantExpression extends ConstantExpression {
   final PrimitiveConstantValue value;
 
   PrimitiveConstantExpression(this.value);
 
   /// The primitive value of this contant expression.
   get primitiveValue;
 }
 
@@ skipping 1227 matching lines @@
   @override
   void visitStringFromEnvironment(StringFromEnvironmentConstantExpression exp,
                                   [_]) {
     sb.write('const String.fromEnvironment("${exp.name}", defaultValue: ');
     visit(exp.defaultValue);
     sb.write(')');
   }
 
   String toString() => sb.toString();
 }