Cleanup the namer, and add a test with fields that used to clash with internal names used by the co…

sdk/lib/_internal/compiler/implementation/js_backend/minify_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 MinifyNamer extends Namer {
   MinifyNamer(Compiler compiler) : super(compiler) {
     reserveBackendNames();
   }
 
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
 
   const ALPHABET_CHARACTERS = 52;  // a-zA-Z.
   const ALPHANUMERIC_CHARACTERS = 62;  // a-zA-Z0-9.
 
   // You can pass an invalid identifier to this and unlike its non-minifying
   // counterpart it will never return the proposedName as the new fresh name.
-  String getFreshName(String proposedName, Set<String> usedNames) {
+  String getFreshName(String proposedName,
+                      Set<String> usedNames,
+                      {bool ensureSafe: true}) {
     var freshName = _getUnusedName(proposedName, usedNames);
     usedNames.add(freshName);
     return freshName;
   }
 
   SourceString getClosureVariableName(SourceString name, int id) {
     if (id < ALPHABET_CHARACTERS) {
       return new SourceString(new String.fromCharCodes([_letterNumber(id)]));
     }
     return new SourceString("${getMappedInstanceName('closure')}_$id");
   }
 
   void reserveBackendNames() {
-    for (var name in JsNames.reservedNativeProperties) {
+     // TODO(7554): We need a complete list from the DOM.
+    const reservedNativeProperties = const <String>["x", "y", "z"];
+    for (var name in reservedNativeProperties) {
       if (name.length < 3) {
         instanceNameMap[name] = name;
       }
       usedInstanceNames.add(name);
     }
   }
 
   // This gets a minified name based on a hash of the proposed name.  This
   // is slightly less efficient than just getting the next name in a series,
   // but it means that small changes in the input program will give smallish
@@ skipping 68 matching lines @@
   }
 
   int _alphaNumericNumber(int x) {
     if (x >= ALPHANUMERIC_CHARACTERS) x %= ALPHANUMERIC_CHARACTERS;
     if (x < 26) return $a + x;
     if (x < 52) return $A + x - 26;
     return $0 + x - 52;
   }
 
 }