Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/htmlcollection_test.dart

 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 bool isChecked(Element e) => (e as CheckboxInputElement).checked;
 bool isUnchecked(Element e) => !(e as CheckboxInputElement).checked;
 
 // Test that List<Element> implements List<T>
 main() {
   Element insertTestDiv() {
     Element element = new Element.tag('div');
     element.innerHtml = r"""
 <div id='allChecked'>
@@ skipping 254 matching lines @@
     expect(someChecked.lastIndexOf(someChecked[3], 2), -1);
 
     expect(someChecked.lastIndexOf(noneChecked[0], 3), -1);
     expect(noneChecked.lastIndexOf(someChecked[0], 3), -1);
     expect(someChecked.lastIndexOf(noneChecked[1], 3), -1);
     expect(noneChecked.lastIndexOf(someChecked[1], 3), -1);
 
     root.remove();
   });
 }