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

sdk/lib/_internal/compiler/implementation/elements/elements.dart

Index: sdk/lib/_internal/compiler/implementation/elements/elements.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/elements.dart b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
index 6e8580a1d2eeb95fe7ea10ad142aa7d511a9c8f8..18a13905255472557728d422f7f410d81b9df259 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/elements.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
@@ -462,8 +462,7 @@ class Elements {
 
   static bool isListSupertype(Element element, Compiler compiler) {
     LibraryElement coreLibrary = compiler.coreLibrary;
-    return (element == coreLibrary.find(const SourceString('Collection')))
-        || (element == coreLibrary.find(const SourceString('Iterable')));
+    return element == coreLibrary.find(const SourceString('Iterable'));
   }
 
   /// A `compareTo` function that places [Element]s in a consistent order based