Remove dart backend

test/dart_codegen/expect/core/num.dart

-part of dart.core;
- abstract class num implements Comparable<num> {bool operator ==(Object other);
- int get hashCode;
- int compareTo(num other);
- num operator +(num other);
- num operator -(num other);
- num operator *(num other);
- num operator %(num other);
- double operator /(num other);
- int operator ~/(num other);
- num operator -();
- num remainder(num other);
- bool operator <(num other);
- bool operator <=(num other);
- bool operator >(num other);
- bool operator >=(num other);
- bool get isNaN;
- bool get isNegative;
- bool get isInfinite;
- bool get isFinite;
- num abs();
- num get sign;
- int round();
- int floor();
- int ceil();
- int truncate();
- double roundToDouble();
- double floorToDouble();
- double ceilToDouble();
- double truncateToDouble();
- num clamp(num lowerLimit, num upperLimit);
- int toInt();
- double toDouble();
- String toStringAsFixed(int fractionDigits);
- String toStringAsExponential([int fractionDigits]);
- String toStringAsPrecision(int precision);
- String toString();
- static num parse(String input, [num onError(String input)]) {
-  String source = input.trim();
-   _parseError = false;
-   num result = int.parse(source, onError: _onParseErrorInt);
-   if (!_parseError) return result;
-   _parseError = false;
-   result = double.parse(source, _onParseErrorDouble);
-   if (!_parseError) return result;
-   if (onError == null) throw new FormatException(input);
-   return onError(input);
-  }
- static bool _parseError = false;
- static int _onParseErrorInt(String _) {
-  _parseError = true;
-   return 0;
-  }
- static double _onParseErrorDouble(String _) {
-  _parseError = true;
-   return 0.0;
-  }
-}