Refactor runtime into libraries, better type reps

tool/sdk_expected_errors.txt

 warning: line 80, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] JS('var', r'#.pop()', this) (dynamic) will need runtime check to cast to type E
     return JS('var', r'#.pop()', this);
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 125, column 9 of dart:_interceptors/js_array.dart: [DownCastComposite] JS('', '#[#]', this, i) (dynamic) will need runtime check to cast to type E
       f(JS('', '#[#]', this, i));
         ^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 161, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] IterableMixinWorkaround.reduce(this, combine) (dynamic) will need runtime check to cast to type E
     return IterableMixinWorkaround.reduce(this, combine);
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 169, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] IterableMixinWorkaround.firstWhere(this, test, orElse) (dynamic) will need runtime check to cast to type E
@@ skipping 655 matching lines @@
                                                          ^^^^^^
 warning: line 357, column 29 of dart:_isolate_helper/isolate_serialization.dart: [DownCastImplicit] fields (List<dynamic>) will need runtime check to cast to type JSArray<dynamic>
     deserializeArrayInPlace(fields);
                             ^^^^^^
 warning: line 20, column 39 of dart:async/async_error.dart: [DownCastImplicit] errorHandler (Function) will need runtime check to cast to type (dynamic) → dynamic
     return zone.registerUnaryCallback(errorHandler);
                                       ^^^^^^^^^^^^
 severe: line 211, column 38 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_next' is not defined for the class 'StreamSubscription<T>'
       assert(!identical(subscription._next, subscription));
                                      ^^^^^
+severe: line 209, column 20 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The method '_setRemoveAfterFiring' is not defined for the class 'StreamSubscription<T>'
+      subscription._setRemoveAfterFiring();
+                   ^^^^^^^^^^^^^^^^^^^^^
 severe: line 207, column 36 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_next' is not defined for the class 'StreamSubscription<T>'
     assert(!identical(subscription._next, subscription));
                                    ^^^^^
-severe: line 209, column 20 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The method '_setRemoveAfterFiring' is not defined for the class 'StreamSubscription<T>'
-      subscription._setRemoveAfterFiring();
-                   ^^^^^^^^^^^^^^^^^^^^^
 severe: line 208, column 22 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_isFiring' is not defined for the class 'StreamSubscription<T>'
     if (subscription._isFiring) {
                      ^^^^^^^^^
 severe: line 206, column 32 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_next' is not defined for the class 'StreamSubscription<T>'
     if (identical(subscription._next, subscription)) return null;
                                ^^^^^
 warning: line 8, column 67 of dart:async/broadcast_stream_controller.dart: [DownCastComposite] controller (_StreamControllerLifecycle<dynamic>) will need runtime check to cast to type _StreamControllerLifecycle<T>
   _BroadcastStream(_StreamControllerLifecycle controller) : super(controller);
                                                                   ^^^^^^^^^^
 warning: line 36, column 15 of dart:async/broadcast_stream_controller.dart: [DownCastComposite] controller (_StreamControllerLifecycle<dynamic>) will need runtime check to cast to type _StreamControllerLifecycle<T>
@@ skipping 76 matching lines @@
                                                      ^^^^^^^^^^^^^
 warning: line 66, column 61 of dart:async/schedule_microtask.dart: [DownCastComposite] callback (dynamic) will need runtime check to cast to type () → void
     _nextCallback = _lastCallback = new _AsyncCallbackEntry(callback);
                                                             ^^^^^^^^
 warning: line 71, column 60 of dart:async/schedule_microtask.dart: [DownCastComposite] callback (dynamic) will need runtime check to cast to type () → void
     _AsyncCallbackEntry newEntry = new _AsyncCallbackEntry(callback);
                                                            ^^^^^^^^
 warning: line 84, column 55 of dart:async/schedule_microtask.dart: [DownCastComposite] callback (dynamic) will need runtime check to cast to type () → void
   _AsyncCallbackEntry entry = new _AsyncCallbackEntry(callback);
                                                       ^^^^^^^^
-severe: line 321, column 34 of dart:async/stream.dart: [AnalyzerError] The getter '_addError' is not defined for the class 'StreamController'
-      final addError = eventSink._addError;
-                                 ^^^^^^^^^
 severe: line 1227, column 17 of dart:async/stream.dart: [AnalyzerError] The method '_addError' is not defined for the class 'StreamController'
       eventSink._addError(error, stackTrace);  // Avoid Zone error replacement.
                 ^^^^^^^^^
 severe: line 396, column 30 of dart:async/stream.dart: [AnalyzerError] The getter '_addError' is not defined for the class 'StreamController'
           onError: eventSink._addError,  // Avoid Zone error replacement.
                              ^^^^^^^^^
+severe: line 321, column 34 of dart:async/stream.dart: [AnalyzerError] The getter '_addError' is not defined for the class 'StreamController'
+      final addError = eventSink._addError;
+                                 ^^^^^^^^^
 warning: line 90, column 25 of dart:async/stream.dart: [DownCastComposite] value (dynamic) will need runtime check to cast to type T
         controller._add(value);
                         ^^^^^
 warning: line 217, column 41 of dart:async/stream.dart: [DownCastComposite] mapSink ((EventSink<T>) → EventSink<dynamic>) will need runtime check to cast to type (EventSink<dynamic>) → EventSink
     return new _BoundSinkStream(source, mapSink);
                                         ^^^^^^^
 warning: line 249, column 44 of dart:async/stream.dart: [DownCastComposite] onListen ((StreamSubscription<T>) → void) will need runtime check to cast to type (StreamSubscription<dynamic>) → void
     return new _AsBroadcastStream<T>(this, onListen, onCancel);
                                            ^^^^^^^^
 warning: line 249, column 54 of dart:async/stream.dart: [DownCastComposite] onCancel ((StreamSubscription<T>) → void) will need runtime check to cast to type (StreamSubscription<dynamic>) → void
@@ skipping 271 matching lines @@
                       ^^^^^^^^^^^^^^^^
 warning: line 1869, column 12 of dart:core/uri.dart: [DownCastComposite] query.split("&").fold({}, (map, element) {int index = element.indexOf("="); if (index == -1) {if (element != "") {map[decodeQueryComponent(element, encoding: encoding)] = "";}} else if (index != 0) {var key = element.substring(0, index); var value = element.substring(index + 1); map[Uri.decodeQueryComponent(key, encoding: encoding)] = decodeQueryComponent(value, encoding: encoding);} return map;}) (dynamic) will need runtime check to cast to type Map<String, String>
     return query.split("&").fold({}, (map, element) {
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 1901, column 12 of dart:core/uri.dart: [DownCastComposite] bytes.map((byteString) {int byte = int.parse(byteString); if (byte < 0 || byte > 255) {error('each part must be in the range of `0..255`');} return byte;}).toList() (List<dynamic>) will need runtime check to cast to type List<int>
     return bytes
            ^^^^^^
 warning: line 2023, column 12 of dart:core/uri.dart: [DownCastComposite] bytes (List<dynamic>) will need runtime check to cast to type List<int>
     return bytes;
            ^^^^^