Change Set.add to return a boolean indicating success.

tests/corelib/set_test.dart

Index: tests/corelib/set_test.dart
diff --git a/tests/corelib/set_test.dart b/tests/corelib/set_test.dart
index 59b8f1339eb132cc4a85bdd6a51db40e6ccf4581..ebe1f7896b8f95a9d48f6d20ad758f17c1597ae8 100644
--- a/tests/corelib/set_test.dart
+++ b/tests/corelib/set_test.dart
@@ -7,20 +7,20 @@ class SetTest {
   static testMain() {
     Set set = new Set();
     Expect.equals(0, set.length);
-    set.add(1);
+    Expect.equals(true, set.add(1));
     Expect.equals(1, set.length);
     Expect.equals(true, set.contains(1));
 
-    set.add(1);
+    Expect.equals(false, set.add(1));
     Expect.equals(1, set.length);
     Expect.equals(true, set.contains(1));
 
-    set.remove(1);
+    Expect.equals(true, set.remove(1));
     Expect.equals(0, set.length);
     Expect.equals(false, set.contains(1));
 
     for (int i = 0; i < 10; i++) {
-      set.add(i);
+      Expect.equals(true, set.add(i));
     }
 
     Expect.equals(10, set.length);
@@ -114,7 +114,7 @@ class SetTest {
 
     Expect.equals(true, set.some(testSome));
     Expect.equals(true, filtered.some(testSome));
-    filtered.remove(4);
+    Expect.equals(true, filtered.remove(4));
     Expect.equals(false, filtered.some(testSome));
 
     // Test Set.intersection.
@@ -161,7 +161,7 @@ class SetTest {
     // Test Set.clear.
     set.clear();
     Expect.equals(0, set.length);
-    set.add(11);
+    Expect.equals(true, set.add(11));
     Expect.equals(1, set.length);
   }
 }