Ensure that unmangled private names are unique.

sdk/lib/_internal/compiler/implementation/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 341 matching lines @@
   /**
    * If the [name] is not private returns [:name:]. Otherwise
    * mangles the [name] so that each library has a unique name.
    */
   String privateName(LibraryElement library, String name) {
     // Public names are easy.
     String nameString = name;
     if (!isPrivateName(name)) return nameString;
 
     // The first library asking for a short private name wins.
-    LibraryElement owner = shouldMinify
-        ? library
-        : shortPrivateNameOwners.putIfAbsent(nameString, () => library);
+    LibraryElement owner =
+        shortPrivateNameOwners.putIfAbsent(nameString, () => library);
 
-    if (owner == library && !shouldMinify && !nameString.contains('\$')) {
+    if (owner == library && !nameString.contains('\$')) {
       // Since the name doesn't contain $ it doesn't clash with any
       // of the private names that have the library name as the prefix.
       return nameString;
     } else {
       // Make sure to return a private name that starts with _ so it
       // cannot clash with any public names.
       String libraryName = getNameOfLibrary(library);
       return '_$libraryName\$$nameString';

[floitsch, 2014/07/29 14:22:39]

Is the libraryName the unminified name of the library? If yes, should we minify
it in minified mode?

[herhut, 2014/07/29 14:31:55]

It is the minified name. However, we do not minify the [nameString] part, as
otherwise error messages would become somewhat meaningless. One could say the
same about the [libraryName] part but I think it is less severe there and we
currently do not report library names in most cases anyway.

     }
   }
 
   String instanceMethodName(FunctionElement element) {
     // TODO(ahe): Could this be: return invocationName(new
     // Selector.fromElement(element))?
     String elementName = element.name;
     String name = operatorNameToIdentifier(elementName);
     if (name != elementName) return getMappedOperatorName(name);
 
@@ skipping 986 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(parameter);
         first = true;
       }
     }
   }
 }