Remove Collection, Collections and clean up List/Set/Queue implementations of retain/remove.

sdk/lib/_internal/compiler/implementation/universe/function_set.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 universe;
 
 // TODO(kasperl): This actually holds getters and setters just fine
 // too and stricly they aren't functions. Maybe this needs a better
 // name -- something like ElementSet seems a bit too generic.
 class FunctionSet {
@@ skipping 55 matching lines @@
 
 class FunctionSetNode {
   final SourceString name;
   final Map<Selector, FunctionSetQuery> cache =
       new Map<Selector, FunctionSetQuery>();
 
   // Initially, we keep the elements in a list because it is more
   // compact than a hash set. Once we get enough elements, we change
   // the representation to be a set to get faster contains checks.
   static const int MAX_ELEMENTS_IN_LIST = 8;
-  Collection<Element> elements = <Element>[];
+  var elements = <Element>[];
   bool isList = true;
 
   FunctionSetNode(this.name);
 
   void add(Element element) {
     assert(element.name == name);
     // We try to avoid clearing the cache unless we have to. For that
     // reason we keep the explicit contains check even though the add
     // method ends up doing the work again (for sets).
     if (!elements.contains(element)) {
@@ skipping 63 matching lines @@
                             Selector selector,
                             Compiler compiler) {
     return new FunctionSetQuery(functions);
   }
 }
 
 class FunctionSetQuery {
   final List<Element> functions;
   const FunctionSetQuery(this.functions);
 }