Incremental compiler: support optional arguments.

dart/pkg/compiler/lib/src/js_emitter/old_emitter/container_builder.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.
 
 part of dart2js.js_emitter;
 
 /// This class should morph into something that makes it easy to build
 /// JavaScript representations of libraries, class-sides, and instance-sides.
 /// Initially, it is just a placeholder for code that is moved from
 /// [CodeEmitterTask].
@@ skipping 345 matching lines @@
 
     FunctionSignature parameters = member.functionSignature;
     bool needsStubs = !parameters.optionalParameters.isEmpty;
     bool canTearOff = false;
     bool isClosure = false;
     bool isNotApplyTarget = !member.isFunction ||
                             member.isConstructor ||
                             member.isAccessor;
     String tearOffName;
 
-    final bool canBeReflected = backend.isAccessibleByReflection(member);
+
+    final bool canBeReflected = backend.isAccessibleByReflection(member) ||
+        // During incremental compilation, we have to assume that reflection
+        // *might* get enabled.
+        compiler.hasIncrementalSupport;
 
     if (isNotApplyTarget) {
       canTearOff = false;
     } else if (member.isInstanceMember) {
       if (member.enclosingClass.isClosure) {
         canTearOff = false;
         isClosure = true;
       } else {
         // Careful with operators.
         canTearOff =
@@ skipping 285 matching lines @@
     assert(needsStubs != null);
     assert(canTearOff != null);
     assert(isClosure != null);
     assert(tearOffName != null || !canTearOff);
     assert(canBeReflected != null);
     assert(canBeApplied != null);
     assert(hasSuperAlias != null);
     assert(needStructuredInfo != null);
   }
 }