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

sdk/lib/_internal/compiler/implementation/js_backend/backend.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 js_backend;
 
 typedef void Recompile(Element element);
 
 class ReturnInfo {
   HType returnType;
@@ skipping 716 matching lines @@
   // explicit receiver.  https://code.google.com/p/dart/issues/detail?id=8942
 
   /**
    * A map of specialized versions of the [getInterceptorMethod].
    * Since [getInterceptorMethod] is a hot method at runtime, we're
    * always specializing it based on the incoming type. The keys in
    * the map are the names of these specialized versions. Note that
    * the generic version that contains all possible type checks is
    * also stored in this map.
    */
-  final Map<String, Collection<ClassElement>> specializedGetInterceptors;
+  final Map<String, Set<ClassElement>> specializedGetInterceptors;
 
   /**
    * Set of classes whose methods are intercepted.
    */
   final Set<ClassElement> interceptedClasses = new Set<ClassElement>();
 
   /**
    * Set of classes used as mixins on native classes.  Methods on these classes
    * might also be mixed in to non-native classes.
    */
@@ skipping 12 matching lines @@
   final RuntimeTypes rti;
 
   JavaScriptBackend(Compiler compiler, bool generateSourceMap, bool disableEval)
       : namer = determineNamer(compiler),
         returnInfo = new Map<Element, ReturnInfo>(),
         invalidateAfterCodegen = new List<Element>(),
         usedInterceptors = new Set<Selector>(),
         oneShotInterceptors = new Map<String, Selector>(),
         interceptedElements = new Map<SourceString, Set<Element>>(),
         rti = new RuntimeTypes(compiler),
-        specializedGetInterceptors =
-            new Map<String, Collection<ClassElement>>(),
+        specializedGetInterceptors = new Map<String, Set<ClassElement>>(),
         super(compiler, JAVA_SCRIPT_CONSTANT_SYSTEM) {
     emitter = disableEval
         ? new CodeEmitterNoEvalTask(compiler, namer, generateSourceMap)
         : new CodeEmitterTask(compiler, namer, generateSourceMap);
     builder = new SsaBuilderTask(this);
     optimizer = new SsaOptimizerTask(this);
     generator = new SsaCodeGeneratorTask(this);
     argumentTypes = new ArgumentTypesRegistry(this);
     fieldTypes = new FieldTypesRegistry(this);
   }
@@ skipping 983 matching lines @@
   ClassElement get constListImplementation => jsArrayClass;
   ClassElement get fixedListImplementation => jsFixedArrayClass;
   ClassElement get growableListImplementation => jsExtendableArrayClass;
   ClassElement get mapImplementation => mapLiteralClass;
   ClassElement get constMapImplementation => constMapLiteralClass;
   ClassElement get functionImplementation => jsFunctionClass;
   ClassElement get typeImplementation => typeLiteralClass;
   ClassElement get boolImplementation => jsBoolClass;
   ClassElement get nullImplementation => jsNullClass;
 }