All strong mode cleaning of dart2js.

pkg/compiler/lib/src/deferred_load.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 deferred_load;
 
 import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
 import 'compiler.dart' show Compiler;
 import 'constants/expressions.dart' show ConstantExpression;
@@ skipping 52 matching lines @@
   /// `true` if this output unit is for the main output file.
   final bool isMainOutput;
 
   /// A unique name representing this [OutputUnit].
   String name;
 
   OutputUnit({this.isMainOutput: false});
 
   String toString() => "OutputUnit($name)";
 
-  bool operator ==(OutputUnit other) {
-    return imports.length == other.imports.length &&
+  bool operator ==(other) {
+    return other is OutputUnit &&
+        imports.length == other.imports.length &&
         imports.containsAll(other.imports);
   }
 
   int get hashCode {
     int sum = 0;
     for (_DeferredImport import in imports) {
       sum = (sum + import.hashCode) & 0x3FFFFFFF; // Stay in 30 bit range.
     }
     return sum;
   }
@@ skipping 1017 matching lines @@
 
   bool operator ==(other) {
     if (other is! _DeclaredDeferredImport) return false;
     return declaration == other.declaration;
   }
 
   int get hashCode => declaration.hashCode * 17;
 
   String toString() => '$declaration';
 }