Warn when adding something to a closed sink and improve documentation

sdk/lib/core/sink.dart

Index: sdk/lib/core/sink.dart
diff --git a/sdk/lib/core/sink.dart b/sdk/lib/core/sink.dart
index 0d8f2eff254a9528e114c2d0d083265b617b0f52..665dab11b1484f6df0e5a76b8146486b850071e0 100644
--- a/sdk/lib/core/sink.dart
+++ b/sdk/lib/core/sink.dart
@@ -14,18 +14,18 @@ part of dart.core;
  */
 abstract class Sink<T> {
   /**
-   * Put the data into the sink.
+   * Puts the [data] into the sink.

[Lasse Reichstein Nielsen, 2017/04/26 08:26:19]

Change Puts-into into Adds-to. Or maybe "Pass-to"

It's a silly documentation anyway - it just repeats the method name, but I guess
that's the cost of being completely generic.

[floitsch, 2017/05/01 16:46:25]

I'm ok with repeating the name, if there is more dartdoc.
done.

    *
    * Must not be called after a call to [close].
    */
   void add(T data);
 
   /**
-   * Tell the sink that no further data will be added.
-   *
-   * Calling this method more than once is allowed, but does nothing.
+   * Closes the sink.
    *
    * The [add] method must not be called after this method.
+   *
+   * Calling this method more than once is allowed, but does nothing.
    */
   void close();
 }