Added Uint8ClampedList. COmpielr optimziations to follow in next CL.

sdk/lib/scalarlist/byte_arrays.dart

 // Copyright (c) 2012, 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.
 
 /**
  * A random-access sequence of bytes that also provides random access to
  * the fixed-width integers and floating point numbers represented by
  * those bytes. Byte arrays may be used to pack and unpack data from
  * external sources (such as networks or files systems), and to process
  * large quantities of numerical data more efficiently than would be possible
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    * array and vice versa. If the [start] index of the region is not specified,
    * it defaults to zero (the first byte in the byte array). If the length is
    * not specified, it defaults to null, which indicates that the view extends
    * to the end of the byte array.
    */
   external factory Uint8List.view(ByteArray array, [int start, int length]);
 }
 
 
 /**
+ * A fixed-length list of 8-bit unsigned integers that is viewable as a
+ * [ByteArray]. For long lists, this implementation will be considerably
+ * more space- and time-efficient than the default [List] implementation.
+ * Indexed store clamps the value to range 0..0xFF.
+ */
+abstract class Uint8ClampedList implements List<int>, ByteArrayViewable {
+  /**
+   * Creates a [Uint8ClampedList] of the specified length (in elements), all of
+   * whose elements are initially zero.
+   */
+  external factory Uint8ClampedList(int length);
+
+  /**
+   * Creates a [Uint8ClampedList] _view_ of the specified region in the
+   * specified byte [array]. Changes in the [Uint8List] will be visible in the
+   * byte array and vice versa. If the [start] index of the region is not
+   * specified, it defaults to zero (the first byte in the byte array). If the
+   * length is not specified, it defaults to null, which indicates that the view
+   * extends to the end of the byte array.
+   */
+  external factory Uint8ClampedList.view(ByteArray array,
+                                         [int start, int length]);
+}
+
+
+/**
  * A fixed-length list of 16-bit signed integers that is viewable as a
  * [ByteArray]. For long lists, this implementation will be considerably
  * more space- and time-efficient than the default [List] implementation.
  */
 abstract class Int16List implements List<int>, ByteArrayViewable {
   /**
    * Creates an [Int16List] of the specified length (in elements), all of
    * whose elements are initially zero.
    */
   external factory Int16List(int length);
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    * [start] of the region is not divisible by 8. If, however, [array]
    * is a view of another byte array, this constructor will throw
    * [ArgumentError] if the implicit starting position in the
    * "ultimately backing" byte array is not divisible by 8. In plain terms,
    * this constructor throws [ArgumentError] if the specified
    * region does not contain an integral number of "float64s," or if it
    * is not "float64-aligned."
    */
   external factory Float64List.view(ByteArray array, [int start, int length]);
 }