Remove instances of dart:dom_deprecated from outside of lib/html and lib/dom. Part 1 of many.

samples/matrix/matrix_client.dart

Index: samples/matrix/matrix_client.dart
===================================================================
--- samples/matrix/matrix_client.dart	(revision 11641)
+++ samples/matrix/matrix_client.dart	(working copy)
@@ -1,13 +0,0 @@
-// 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.
-
-/**
- * Library definition file for the matrix library for browser
- * applications.  (This imports dart:dom_deprecated because the
- * Matrix4 class uses Float32Array.
- */
-#library("matrix");
-#import("dart:dom_deprecated");
-#import("dart:math", prefix: "Math");
-#source("matrix4.dart");