Assign invalid name to globalized closures.

sdk/lib/_internal/compiler/implementation/js_emitter/code_emitter_task.dart

 // Copyright (c) 2012, 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;
 
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
  *
@@ skipping 661 matching lines @@
       if (!mangledName.startsWith(namer.setterPrefix)) return '$name=';
       String base = mangledName.substring(namer.setterPrefix.length);
       String getter = '${namer.getterPrefix}$base';
       mangledFieldNames[getter] = name;
       recordedMangledNames.add(getter);
       // TODO(karlklose,ahe): we do not actually need to store information
       // about the name of this setter in the output, but it is needed for
       // marking the function as invokable by reflection.
       return '$name=';
     }
+    if (elementOrSelector is Element && elementOrSelector.isClosure()) {
+      // Closures are synthesized and their name might conflict with existing
+      // globals. Assign an illegal name, and make sure they don't clash
+      // with each other.
+      return " $mangledName";
+    }
     if (elementOrSelector is Selector
         || elementOrSelector.isFunction()
         || elementOrSelector.isConstructor()) {
       int requiredParameterCount;
       int optionalParameterCount;
       String namedArguments = '';
       bool isConstructor = false;
       if (elementOrSelector is Selector) {
         Selector selector = elementOrSelector;
         requiredParameterCount = selector.argumentCount;
@@ skipping 952 matching lines @@
     String sourceMap = buildSourceMap(mainBuffer, compiledFile);
     compiler.outputProvider(name, 'js.map')
         ..add(sourceMap)
         ..close();
   }
 
   void registerReadTypeVariable(TypeVariableElement element) {
     readTypeVariables.add(element);
   }
 }