Remove uses of unittest in the HTML tests where possible.

pkg/dev_compiler/test/not_yet_strong_tests.dart

 import 'dart:collection';
 
 /// The set of tests that are not yet strong mode safe.
 final notYetStrongTests = new HashSet<String>.from([
   'language/abstract_exact_selector_test_01_multi',
   'language/abstract_factory_constructor_test_00_multi',
   'language/abstract_getter_test_01_multi',
   'language/abstract_runtime_error_test_01_multi',
   'language/abstract_runtime_error_test_02_multi',
   'language/abstract_runtime_error_test_03_multi',
@@ skipping 2418 matching lines @@
   'lib/html/cross_frame_test',
   'lib/html/element_test',
   'lib/html/events_test',
   'lib/html/fileapi_test',
   'lib/html/filereader_test',
   'lib/html/fontface_loaded_test',
   'lib/html/js_function_getter_trust_types_test',
   'lib/html/js_typed_interop_side_cast_exp_test',
   'lib/html/js_typed_interop_side_cast_test',
   'lib/html/keyboard_event_test',
-  'lib/html/localstorage_test',
   'lib/html/mutationobserver_test',
-  'lib/html/node_test',
-  'lib/html/node_validator_important_if_you_suppress_make_the_bug_critical_test',
   'lib/html/postmessage_structured_test',
-  'lib/html/queryall_test',
   'lib/html/resource_http_test',
-  'lib/html/selectelement_test',
-  'lib/html/track_element_constructor_test',
   'lib/html/transferables_test',
-  'lib/html/typed_arrays_range_checks_test',
-  'lib/html/typing_test',
-  'lib/html/unknownelement_test',
   'lib/html/webgl_1_test',
-  'lib/html/window_nosuchmethod_test',
   'lib/html/wrapping_collections_test',
   // TODO(jmesserly): these are both under "dart:html" as well.
   'js_test',
   'js_util_test'
 ]);