Fix ParameterMirror.hasDefaultValue/defaultValue in source mirrors.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import 'elements.dart';
 import '../../compiler.dart' as api;
 import '../tree/tree.dart';
 import '../util/util.dart';
@@ skipping 1151 matching lines @@
     return variables.computeType(compiler);
   }
 
   bool isInstanceMember() => variables.isInstanceMember();
 
   // Note: cachedNode.getBeginToken() will not be correct in all
   // cases, for example, for function typed parameters.
   Token position() => findMyName(variables.position());
 
   accept(ElementVisitor visitor) => visitor.visitVariableElement(this);
+
+  // TODO(johnniwinther): Move the patch/origin implementation to a parameter
+  // specific element when added.
+
+  /**
+   * A function declaration that should be parsed instead of the current one.
+   * The patch should be parsed as if it was in the current scope. Its
+   * signature must match this function's signature.
+   */
+  VariableElementX patch = null;
+  VariableElementX origin = null;
+
+  bool get isPatch => origin != null;
+  bool get isPatched => patch != null;
 }
 
 class FieldElementX extends VariableElementX implements FieldElement {
   List<FunctionElement> nestedClosures = new List<FunctionElement>();
 
   FieldElementX(String name,
                 VariableListElement variables,
                 Expression cachedNode)
     : super(name, variables, ElementKind.FIELD, cachedNode);
 
@@ skipping 1292 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }