Use signature inheritance when method types are unchanged

lib/runtime/dart/math.js

 var math = dart.defineLibrary(math, {});
 var core = dart.import(core);
 var _js_helper = dart.lazyImport(_js_helper);
 (function(exports, core, _js_helper) {
   'use strict';
   class _JenkinsSmiHash extends core.Object {
     static combine(hash, value) {
       hash = 536870911 & dart.notNull(hash) + dart.notNull(value);
       hash = 536870911 & dart.notNull(hash) + ((524287 & dart.notNull(hash)) << 10);
       return dart.notNull(hash) ^ dart.notNull(hash) >> 6;
@@ skipping 58 matching lines @@
       }
       squaredDistanceTo(other) {
         dart.as(other, Point$(T));
         let dx = this.x['-'](other.x);
         let dy = this.y['-'](other.y);
         return dart.as(dart.notNull(dx) * dart.notNull(dx) + dart.notNull(dy) * dart.notNull(dy), T);
       }
     }
     dart.setSignature(Point, {
       methods: () => ({
-        toString: dart.functionType(core.String, []),
-        '==': dart.functionType(core.bool, [dart.dynamic]),
         '+': dart.functionType(Point$(T), [Point$(T)]),
         '-': dart.functionType(Point$(T), [Point$(T)]),
         '*': dart.functionType(Point$(T), [core.num]),
         distanceTo: dart.functionType(core.double, [Point$(T)]),
         squaredDistanceTo: dart.functionType(T, [Point$(T)])
       })
     });
     return Point;
   });
   let Point = Point$();
@@ skipping 64 matching lines @@
       }
       get bottomRight() {
         return new (Point$(T))(dart.as(this.left['+'](this.width), T), dart.as(this.top['+'](this.height), T));
       }
       get bottomLeft() {
         return new (Point$(T))(this.left, dart.as(this.top['+'](this.height), T));
       }
     }
     dart.setSignature(_RectangleBase, {
       methods: () => ({
-        toString: dart.functionType(core.String, []),
-        '==': dart.functionType(core.bool, [dart.dynamic]),
         intersection: dart.functionType(Rectangle$(T), [Rectangle$(T)]),
         intersects: dart.functionType(core.bool, [Rectangle$(core.num)]),
         boundingBox: dart.functionType(Rectangle$(T), [Rectangle$(T)]),
         containsRectangle: dart.functionType(core.bool, [Rectangle$(core.num)]),
         containsPoint: dart.functionType(core.bool, [Point$(core.num)])
       })
     });
     return _RectangleBase;
   });
   let _RectangleBase = _RectangleBase$();
@@ skipping 328 matching lines @@
   exports.sin = sin;
   exports.cos = cos;
   exports.tan = tan;
   exports.acos = acos;
   exports.asin = asin;
   exports.atan = atan;
   exports.sqrt = sqrt;
   exports.exp = exp;
   exports.log = log;
 })(math, core, _js_helper);