Fix bug in trim introduced by rewrite.

tests/corelib/string_trim2_test.dart

Index: tests/corelib/string_trim2_test.dart
diff --git a/tests/corelib/string_trim2_test.dart b/tests/corelib/string_trim2_test.dart
index fc894a25901de46665ef7f48035e8f9e89cac9f8..11379dd77618014c9e72034e4216053b2fd8ee75 100644
--- a/tests/corelib/string_trim2_test.dart
+++ b/tests/corelib/string_trim2_test.dart
@@ -36,14 +36,14 @@ const WHITESPACE = const [
 
 main() {
   for (var ws in WHITESPACE) {
-    Expect.equals("", new String.fromCharCode(ws).trim());
-  }
-  Expect.equals("", new String.fromCharCodes(WHITESPACE).trim());
-  for (var ws in WHITESPACE) {
+    var name = ws.toRadixString(16);
     var c = new String.fromCharCode(ws);
-    Expect.equals("a", ("a" + c).trim());
-    Expect.equals("a", (c + "a").trim());
-    Expect.equals("a", (c + c + "a" + c + c).trim());
-    Expect.equals("a" + c + "a", (c + c + "a" + c + "a" + c + c).trim());
+    Expect.equals("", c.trim(), "$name");
+    Expect.equals("a", ("a" + c).trim(), "a-$name");
+    Expect.equals("a", (c + "a").trim(), "$name-a");
+    Expect.equals("a", (c + c + "a" + c + c).trim(), "$name around");
+    Expect.equals("a" + c + "a", (c + c + "a" + c + "a" + c + c).trim(),
+                  "$name many");
   }
+  Expect.equals("", new String.fromCharCodes(WHITESPACE).trim(), "ALL");
 }