dart:js interop problems.

my_code_snippet.dart

void map(doc, emit) {
  emit(doc); // emit all documents
}

var db = new JsObject(context['PouchDB'], ['test_db']);
var jsPromise = db.callMethod('query', [map]);

// map ends up being wrapped like this:
// function () {       return func(Array.prototype.slice.apply(arguments));   }

pouchdb_snippet.js

// PouchDB is expecting a function like this:
// function(doc, emit) { /* ... */ }
// but Dart is sending this:
// function () {       return func(Array.prototype.slice.apply(arguments));   }
//
// Thus triggers the second branch.
if (typeof view.mapFun === "function" && view.mapFun.length === 2) {
  var origMap = view.mapFun;
  mapFun = function (doc) {
    return origMap(doc, emit);
  };
} else {
  mapFun = evalFunc(view.mapFun.toString(), emit, sum, log, Array.isArray, JSON.parse);
}