Implement operator-is for interfaces' supertypes and String's supertypes. Also, improve stack trace…

dart/frog/leg/lib/js_helper.dart

Index: dart/frog/leg/lib/js_helper.dart
diff --git a/dart/frog/leg/lib/js_helper.dart b/dart/frog/leg/lib/js_helper.dart
index f6964164e1db7280779dc946c3c62350d1def362..145a72243d65e7440d98f639eda9b4a3f637e5ca 100644
--- a/dart/frog/leg/lib/js_helper.dart
+++ b/dart/frog/leg/lib/js_helper.dart
@@ -1172,3 +1172,19 @@ builtin$hashCode$0(receiver) {
 
 // TODO(ahe): Dynamic may be overridden.
 builtin$get$dynamic(receiver) => receiver;
+
+/**
+ * Called by generated code to capture the stacktrace before throwing
+ * an exception.
+ */
+captureStackTrace(ex) {
+  return ex;

[ngeoffray, 2012/02/22 11:12:36]

Remove this line.

[ahe, 2012/02/22 21:51:24]

Done.

+  if (ex === null) return ex;

[ngeoffray, 2012/02/22 11:12:36]

You could change that to:
if (JS('bool', @'typeof $0 !== "object"', ex)) return ex;

[ahe, 2012/02/22 21:51:24]

Great idea!

+  if (JS('bool', @'typeof $0 === "object"', ex)) {
+    var hasCapture = JS('bool', @'!!(Error.captureStackTrace)');
+    if (hasCapture) {
+      JS('Object', @'Error.captureStackTrace($0)', ex);
+    }
+  }
+  return ex;
+}