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

BUG=

Review URL: https://codereview.chromium.org//14173003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/yaml@21338 260f80e4-7a28-3924-810f-c04153c831b5
diff --git a/lib/parser.dart b/lib/parser.dart
index c84f374..9621b13 100644
--- a/lib/parser.dart
+++ b/lib/parser.dart
@@ -1119,7 +1119,7 @@
   });
 
   // 138
-  Collection<_Node> ns_s_flowSeqEntries(int indent, int ctx) {
+  Iterable<_Node> ns_s_flowSeqEntries(int indent, int ctx) {
     var first = ns_flowSeqEntry(indent, ctx);
     if (!truth(first)) return new Queue<_Node>();
     zeroOrOne(() => s_separate(indent, ctx));