Allow Object when doing lookups.

sdk/lib/core/set.dart

Index: sdk/lib/core/set.dart
diff --git a/sdk/lib/core/set.dart b/sdk/lib/core/set.dart
index ff8d4b3aac843b0619dcf97bb5c28ecc4bd11c6d..2d923bfae5834f7c3df33f2667635a3c6606a4ad 100644
--- a/sdk/lib/core/set.dart
+++ b/sdk/lib/core/set.dart
@@ -19,7 +19,7 @@ abstract class Set<E> extends IterableBase<E> {
   /**
    * Returns true if [value] is in the set.
    */
-  bool contains(E value);
+  bool contains(Object value);
 
   /**
    * Adds [value] into the set. The method has no effect if
@@ -66,7 +66,7 @@ abstract class Set<E> extends IterableBase<E> {
   /**
    * Returns true if this Set contains all the elements of [other].
    */
-  bool containsAll(Iterable<E> other);
+  bool containsAll(Iterable<Object> other);
 
   /**
    * Returns a new set which is the intersection between this set and [other].