Fix remaining warnings.

lib/compiler/implementation/native_emitter.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.
 
 class NativeEmitter {
 
   Compiler compiler;
   StringBuffer buffer;
 
   // Classes that participate in dynamic dispatch. These are the
@@ skipping 188 matching lines @@
     Set<ClassElement> seen = new Set<ClassElement>();
     List<ClassElement> classes = <ClassElement>[];
     void visit(ClassElement cls) {
       if (seen.contains(cls)) return;
       seen.add(cls);
       for (final ClassElement subclass in getDirectSubclasses(cls)) {
         visit(subclass);
       }
       classes.add(cls);
     }
-    for (final ClassElement cls in classesWithDynamicDispatch) {
-      visit(cls);
+    for (final ClassElement classElement in classesWithDynamicDispatch) {
+      visit(classElement);
     }
 
     Collection<ClassElement> dispatchClasses = classes.filter(
         (cls) => !getDirectSubclasses(cls).isEmpty() &&
                   classesWithDynamicDispatch.contains(cls));
 
     buffer.add('// ${classes.length} classes\n');
     Collection<ClassElement> classesThatHaveSubclasses = classes.filter(
         (ClassElement t) => !getDirectSubclasses(t).isEmpty());
     buffer.add('// ${classesThatHaveSubclasses.length} !leaf\n');
@@ skipping 11 matching lines @@
     // the test, replacing dozens of HTMLxxxElement classes with the regexp
     // /HTML.*Element/.
 
     // Temporary variables for common substrings.
     List<String> varNames = <String>[];
     // var -> expression
     Map<String, String> varDefns = <String>{};
     // tag -> expression (a string or a variable)
     Map<ClassElement, String> tagDefns = new Map<ClassElement, String>();
 
-    String makeExpression(ClassElement cls) {
+    String makeExpression(ClassElement classElement) {
       // Expression fragments for this set of cls keys.
       List<String> expressions = <String>[];
       // TODO: Remove if cls is abstract.
-      List<String> subtags = [toNativeName(cls)];
+      List<String> subtags = [toNativeName(classElement)];
       void walk(ClassElement cls) {
         for (final ClassElement subclass in getDirectSubclasses(cls)) {
           ClassElement tag = subclass;
           String existing = tagDefns[tag];
           if (existing == null) {
             subtags.add(toNativeName(tag));
             walk(subclass);
           } else {
             if (varDefns.containsKey(existing)) {
               expressions.add(existing);
             } else {
               String varName = 'v${varNames.length}/*${tag}*/';
               varNames.add(varName);
               varDefns[varName] = existing;
               tagDefns[tag] = varName;
               expressions.add(varName);
             }
           }
         }
       }
-      walk(cls);
+      walk(classElement);
       String constantPart = "'${Strings.join(subtags, '|')}'";
       if (constantPart != "''") expressions.add(constantPart);
       String expression;
       if (expressions.length == 1) {
         expression = expressions[0];
       } else {
         expression = "[${Strings.join(expressions, ',')}].join('|')";
       }
       return expression;
     }
 
-    for (final ClassElement cls in dispatchClasses) {
-      tagDefns[cls] = makeExpression(cls);
+    for (final ClassElement classElement in dispatchClasses) {
+      tagDefns[classElement] = makeExpression(classElement);
     }
 
     // Write out a thunk that builds the metadata.
 
     if (!tagDefns.isEmpty()) {
       buffer.add('(function(){\n');
 
       for (final String varName in varNames) {
         buffer.add('  var ${varName} = ${varDefns[varName]};\n');
       }
@@ skipping 63 matching lines @@
     String toStringName = compiler.namer.instanceMethodName(
         null, const SourceString('toString'), 0);
     objectProperties.add("$defPropName(Object.prototype, '$toStringName', ");
     objectProperties.add(
         'function() { return $toStringHelperName(this); });\n');
 
     // Finally, emit the code in the main buffer.
     targetBuffer.add('(function() {\n$objectProperties$buffer\n})();\n');
   }
 }