Remove dart backend

test/dart_codegen/expect/async/schedule_microtask.dart

-part of dart.async;
- typedef void _AsyncCallback();
- class _AsyncCallbackEntry {final _AsyncCallback callback;
- _AsyncCallbackEntry next;
- _AsyncCallbackEntry(this.callback);
-}
- _AsyncCallbackEntry _nextCallback;
- _AsyncCallbackEntry _lastCallback;
- _AsyncCallbackEntry _lastPriorityCallback;
- bool _isInCallbackLoop = false;
- void _asyncRunCallbackLoop() {
-while (_nextCallback != null) {
-  _lastPriorityCallback = null;
-   _AsyncCallbackEntry entry = _nextCallback;
-   _nextCallback = entry.next;
-   if (_nextCallback == null) _lastCallback = null;
-   entry.callback();
-  }
-}
- void _asyncRunCallback() {
-_isInCallbackLoop = true;
- try {
-  _asyncRunCallbackLoop();
-  }
- finally {
-  _lastPriorityCallback = null;
-   _isInCallbackLoop = false;
-   if (_nextCallback != null) _AsyncRun._scheduleImmediate(_asyncRunCallback);
-  }
-}
- void _scheduleAsyncCallback(callback) {
-if (_nextCallback == null) {
-  _nextCallback = _lastCallback = new _AsyncCallbackEntry(DEVC$RT.cast(callback, dynamic, _AsyncCallback, "CompositeCast", """line 66, column 61 of dart:async/schedule_microtask.dart: """, callback is _AsyncCallback, false));
-   if (!_isInCallbackLoop) {
-    _AsyncRun._scheduleImmediate(_asyncRunCallback);
-    }
-  }
- else {
-  _AsyncCallbackEntry newEntry = new _AsyncCallbackEntry(DEVC$RT.cast(callback, dynamic, _AsyncCallback, "CompositeCast", """line 71, column 60 of dart:async/schedule_microtask.dart: """, callback is _AsyncCallback, false));
-   _lastCallback.next = newEntry;
-   _lastCallback = newEntry;
-  }
-}
- void _schedulePriorityAsyncCallback(callback) {
-_AsyncCallbackEntry entry = new _AsyncCallbackEntry(DEVC$RT.cast(callback, dynamic, _AsyncCallback, "CompositeCast", """line 84, column 55 of dart:async/schedule_microtask.dart: """, callback is _AsyncCallback, false));
- if (_nextCallback == null) {
-  _scheduleAsyncCallback(callback);
-   _lastPriorityCallback = _lastCallback;
-  }
- else if (_lastPriorityCallback == null) {
-  entry.next = _nextCallback;
-   _nextCallback = _lastPriorityCallback = entry;
-  }
- else {
-  entry.next = _lastPriorityCallback.next;
-   _lastPriorityCallback.next = entry;
-   _lastPriorityCallback = entry;
-   if (entry.next == null) {
-    _lastCallback = entry;
-    }
-  }
-}
- void scheduleMicrotask(void callback()) {
-if (identical(_ROOT_ZONE, Zone.current)) {
-  _rootScheduleMicrotask(null, null, _ROOT_ZONE, callback);
-   return;}
- Zone.current.scheduleMicrotask(Zone.current.bindCallback(callback, runGuarded: true));
-}
- class _AsyncRun {external static void _scheduleImmediate(void callback());
-}