[sdk] Followup to 13978f8

Address remaining comments from Lasse for `SendPort.send`.

Change-Id: I7fead8aeea9af16cc252b5ddc1bc8cb4d2ffae3d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/276526
Reviewed-by: Lasse Nielsen <[email protected]>
Commit-Queue: Slava Egorov <[email protected]>

Author: mraleph

sdk/lib/isolate/isolate.dart

@@ -720,7 +720,9 @@ abstract class SendPort implements Capability {
   ///     - [List], [Map], [LinkedHashMap], [Set] and [LinkedHashSet]
   ///     - [TransferableTypedData]
   ///     - [Capability]
-  ///   - [SendPort] instances returned by [ReceivePort]'s `sendPort` getter
+  ///   - [SendPort] instances from [ReceivePort.sendPort] or
+  ///     [RawReceivePort.sendPort] where the receive ports are created
+  ///     using those classes' constructors.
   ///   - Instances of [Type] representing one of the types mentioned above,
   ///     `Object`, `dynamic`, `void` and `Never` as well as nullable variants
   ///     of all these types. For generic types type arguments must be sendable