Remove use of deprecated test functions.

tests/html/dom_isolates_test.dart

Index: tests/html/dom_isolates_test.dart
===================================================================
--- tests/html/dom_isolates_test.dart	(revision 10086)
+++ tests/html/dom_isolates_test.dart	(working copy)
@@ -53,10 +53,10 @@
   });
 
   test('Null as target window', () {
-    expectThrow(() => spawnDomIsolate(null, 'isolateMain'));
+    expect(() => spawnDomIsolate(null, 'isolateMain'), throws);
   });
 
   test('Not window as target window', () {
-    expectThrow(() => spawnDomIsolate(document, 'isolateMain'));
+    expect(() => spawnDomIsolate(document, 'isolateMain'), throws);
   });
 }