Convert some for-in loops for performance

pkg/analyzer/lib/src/generated/element_resolver.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 analyzer.src.generated.element_resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 452 matching lines @@
   Object visitFunctionTypedFormalParameter(FunctionTypedFormalParameter node) {
     _resolveMetadataForParameter(node.element, node);
     return null;
   }
 
   @override
   Object visitImportDirective(ImportDirective node) {
     SimpleIdentifier prefixNode = node.prefix;
     if (prefixNode != null) {
       String prefixName = prefixNode.name;
-      for (PrefixElement prefixElement in _definingLibrary.prefixes) {
+      List<PrefixElement> prefixes = _definingLibrary.prefixes;
+      int count = prefixes.length;
+      for (int i = 0; i < count; i++) {
+        PrefixElement prefixElement = prefixes[i];
         if (prefixElement.displayName == prefixName) {
           prefixNode.staticElement = prefixElement;
           break;
         }
       }
     }
     ImportElement importElement = node.element;
     if (importElement != null) {
       // The element is null when the URI is invalid
       LibraryElement library = importElement.importedLibrary;
@@ skipping 900 matching lines @@
       !(element is ClassElement && element.isOrInheritsProxy);
 
   /**
    * Look for any declarations of the given [identifier] that are imported using
    * a prefix. Return the element that was found, or `null` if the name is not
    * imported using a prefix.
    */
   Element _findImportWithoutPrefix(SimpleIdentifier identifier) {
     Element element = null;
     Scope nameScope = _resolver.nameScope;
-    for (ImportElement importElement in _definingLibrary.imports) {
+    List<ImportElement> imports = _definingLibrary.imports;
+    int length = imports.length;
+    for (int i = 0; i < length; i++) {
+      ImportElement importElement = imports[i];
       PrefixElement prefixElement = importElement.prefix;
       if (prefixElement != null) {
         Identifier prefixedIdentifier = new PrefixedIdentifierImpl.temp(
             new SimpleIdentifierImpl(new StringToken(TokenType.STRING,
                 prefixElement.name, prefixElement.nameOffset)),
             identifier);
         Element importedElement =
             nameScope.lookup(prefixedIdentifier, _definingLibrary);
         if (importedElement != null) {
           if (element == null) {
@@ skipping 1182 matching lines @@
 
   @override
   Element get staticElement => null;
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) => null;
 
   @override
   void visitChildren(AstVisitor visitor) {}
 }