Add --modules=node support

lib/runtime/dart/math.js

 dart_library.library('dart/math', null, /* Imports */[
   'dart/_runtime',
   'dart/core'
 ], /* Lazy imports */[
   'dart/_js_helper'
 ], function(exports, dart, core, _js_helper) {
   'use strict';
   let dartx = dart.dartx;
   class _JenkinsSmiHash extends core.Object {
     static combine(hash, value) {
@@ skipping 70 matching lines @@
       methods: () => ({
         '+': [Point$(T), [Point$(T)]],
         '-': [Point$(T), [Point$(T)]],
         '*': [Point$(T), [core.num]],
         distanceTo: [core.double, [Point$(T)]],
         squaredDistanceTo: [T, [Point$(T)]]
       })
     });
     return Point;
   });
-  let Point = Point$();
+  const Point = Point$();
   class Random extends core.Object {
     static new(seed) {
       if (seed === void 0) seed = null;
       return seed == null ? dart.const(new _JSRandom()) : new _Random(seed);
     }
   }
   dart.setSignature(Random, {
     constructors: () => ({new: [Random, [], [core.int]]})
   });
   const _RectangleBase$ = dart.generic(function(T) {
@@ skipping 64 matching lines @@
       methods: () => ({
         intersection: [Rectangle$(T), [Rectangle$(T)]],
         intersects: [core.bool, [Rectangle$(core.num)]],
         boundingBox: [Rectangle$(T), [Rectangle$(T)]],
         containsRectangle: [core.bool, [Rectangle$(core.num)]],
         containsPoint: [core.bool, [Point$(core.num)]]
       })
     });
     return _RectangleBase;
   });
-  let _RectangleBase = _RectangleBase$();
+  const _RectangleBase = _RectangleBase$();
   const Rectangle$ = dart.generic(function(T) {
     class Rectangle extends _RectangleBase$(T) {
       Rectangle(left, top, width, height) {
         this.left = left;
         this.top = top;
         this.width = dart.notNull(width) < 0 ? -dart.notNull(width) * 0 : width;
         this.height = dart.notNull(height) < 0 ? -dart.notNull(height) * 0 : height;
         super._RectangleBase();
       }
       static fromPoints(a, b) {
         let left = min(a.x, b.x);
         let width = dart.notNull(max(a.x, b.x)) - dart.notNull(left);
         let top = min(a.y, b.y);
         let height = dart.notNull(max(a.y, b.y)) - dart.notNull(top);
         return new (Rectangle$(T))(left, top, width, height);
       }
     }
     dart.setSignature(Rectangle, {
       constructors: () => ({
         Rectangle: [Rectangle$(T), [T, T, T, T]],
         fromPoints: [Rectangle$(T), [Point$(T), Point$(T)]]
       })
     });
     return Rectangle;
   });
-  let Rectangle = Rectangle$();
+  const Rectangle = Rectangle$();
   const _width = Symbol('_width');
   const _height = Symbol('_height');
   const MutableRectangle$ = dart.generic(function(T) {
     class MutableRectangle extends _RectangleBase$(T) {
       MutableRectangle(left, top, width, height) {
         this.left = left;
         this.top = top;
         this[_width] = dart.notNull(width) < 0 ? _clampToZero(width) : width;
         this[_height] = dart.notNull(height) < 0 ? _clampToZero(height) : height;
         super._RectangleBase();
@@ skipping 24 matching lines @@
     }
     MutableRectangle[dart.implements] = () => [Rectangle$(T)];
     dart.setSignature(MutableRectangle, {
       constructors: () => ({
         MutableRectangle: [MutableRectangle$(T), [T, T, T, T]],
         fromPoints: [MutableRectangle$(T), [Point$(T), Point$(T)]]
       })
     });
     return MutableRectangle;
   });
-  let MutableRectangle = MutableRectangle$();
+  const MutableRectangle = MutableRectangle$();
   function _clampToZero(value) {
     dart.assert(dart.notNull(value) < 0);
     return -dart.notNull(value) * 0;
   }
   dart.fn(_clampToZero, core.num, [core.num]);
   const E = 2.718281828459045;
   const LN10 = 2.302585092994046;
   const LN2 = 0.6931471805599453;
   const LOG2E = 1.4426950408889634;
   const LOG10E = 0.4342944819032518;
@@ skipping 244 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;
 });