Apply updates to static methods.

dart/pkg/dart2js_incremental/lib/diff.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 trydart.poi.diff;
 
 import 'package:compiler/implementation/elements/elements.dart' show
     AbstractFieldElement,
     ClassElement,
     CompilationUnitElement,
@@ skipping 13 matching lines @@
     ErrorToken,
     IDENTIFIER_TOKEN,
     KEYWORD_TOKEN,
     PartialClassElement,
     PartialElement,
     Token;
 
 class Difference {
   final DeclarationSite before;
   final DeclarationSite after;
+
+  /// Records the position of first difference between [before] and [after]. If
+  /// either [before] or [after] are null, [token] is null.
   Token token;
 
-  Difference(this.before, this.after);
+  Difference(this.before, this.after) {
+    if (before == after) {
+      throw '[before] and [after] are the same.';
+    }
+  }
 
   String toString() {
     if (before == null) return 'Added($after)';
     if (after == null) return 'Removed($before)';
     return 'Modified($after -> $before)';
   }
 }
 
 List<Difference> computeDifference(
     ScopeContainerElement before,
     ScopeContainerElement after) {
   Map<String, DeclarationSite> beforeMap = <String, DeclarationSite>{};
   before.forEachLocalMember((modelx.ElementX element) {
     DeclarationSite site = element.declarationSite;
-    assert(site != null);
-    beforeMap[element.name] = site;
+    assert(site != null || element.isSynthesized);
+    if (!element.isSynthesized) {
+      beforeMap[element.name] = site;
+    }
   });
   List<Difference> modifications = <Difference>[];
   List<Difference> potentiallyChanged = <Difference>[];
   after.forEachLocalMember((modelx.ElementX element) {
     DeclarationSite existing = beforeMap.remove(element.name);
     if (existing == null) {
       modifications.add(new Difference(null, element.declarationSite));
     } else {
       potentiallyChanged.add(new Difference(existing, element.declarationSite));
     }
@@ skipping 37 matching lines @@
       beforeToken = beforeToken.next;
       afterToken = afterToken.next;
       beforeKind = beforeToken.kind;
       afterKind = afterToken.kind;
     }
     return beforeKind != afterKind;
   }
   print("$before isn't a PartialElement");
   return true;
 }