Update documentation comments.

lib/src/hash.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library crypto.hash;
 
-/**
- * Interface for cryptographic hash functions.
- *
- * The [add] method is used to add data to the hash. The [close] method
- * is used to extract the message digest.
- *
- * Once the [close] method has been called no more data can be added using the
- * [add] method. If [add] is called after the first call to [close] a
- * HashException is thrown.
- *
- * If multiple instances of a given Hash is needed the [newInstance]
- * method can provide a new instance.
- */
+/// An interface for cryptographic hash functions.
+///
+/// The [add] method adds data to the hash. The [close] method extracts the
+/// message digest.
+///
+/// If multiple instances of a given Hash is needed, the [newInstance] method
+/// can provide a new instance.
 // TODO(floitsch): make Hash implement Sink, EventSink or similar.
 abstract class Hash {
-  /**
-   * Add a list of bytes to the hash computation.
-   */
+  /// Add a list of bytes to the hash computation.
+  ///
+  /// If [this] has already been closed, throws a [StateError].
   void add(List<int> data);
 
-  /**
-   * Finish the hash computation and extract the message digest as
-   * a list of bytes.
-   */
+  /// Finish the hash computation and extract the message digest as a list of
+  /// bytes.
   List<int> close();
 
-  /**
-   * Returns a new instance of this hash function.
-   */
+  /// Returns a new instance of this hash function.
   Hash newInstance();
 
-  /**
-   * Internal block size of the hash in bytes.
-   *
-   * This is exposed for use by the HMAC class which needs to know the
-   * block size for the [Hash] it is using.
-   */
+  /// The internal block size of the hash in bytes.
+  ///
+  /// This is exposed for use by the [HMAC] class, which needs to know the block
+  /// size for the [Hash] it uses.
   int get blockSize;
 }