Add constructors for Float32Array and friends.

client/html/src/Uint8Array.dart

 // Copyright (c) 2011, 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.
 
-// WARNING: Do not edit - generated code.
-
-interface Uint8Array extends ArrayBufferView {
+interface Uint8Array extends ArrayBufferView
+    default Uint8ArrayWrappingImplementation {
 
   static final int BYTES_PER_ELEMENT = 1;
 
+  Uint8Array(int length);
+
+  Uint8Array.from(List<num> list);
+
+  Uint8Array.fromBuffer(ArrayBuffer buffer);
+
   int get length();
 
   Uint8Array subarray(int start, [int end]);
 }