Use destructuring assignments for named parameters (#180)

lib/runtime/dart/_js_helper.js

 dart_library.library('dart/_js_helper', null, /* Imports */[
   "dart/_runtime",
   'dart/core',
   'dart/collection',
   'dart/_interceptors',
   'dart/_foreign_helper'
 ], /* Lazy imports */[
 ], function(exports, dart, core, collection, _interceptors, _foreign_helper) {
   'use strict';
   let dartx = dart.dartx;
@@ skipping 13 matching lines @@
   });
   class Native extends core.Object {
     Native(name) {
       this.name = name;
     }
   }
   dart.setSignature(Native, {
     constructors: () => ({Native: [Native, [core.String]]})
   });
   class JsPeerInterface extends core.Object {
-    JsPeerInterface(opts) {
-      let name = opts && 'name' in opts ? opts.name : null;
+    JsPeerInterface({name = null} = {}) {
       this.name = name;
     }
   }
   dart.setSignature(JsPeerInterface, {
     constructors: () => ({JsPeerInterface: [JsPeerInterface, [], {name: core.String}]})
   });
   class SupportJsExtensionMethods extends core.Object {
     SupportJsExtensionMethods() {
     }
   }
@@ skipping 26 matching lines @@
   let _nativeGlobalRegExp = Symbol('_nativeGlobalRegExp');
   let _nativeAnchoredRegExp = Symbol('_nativeAnchoredRegExp');
   let _isMultiLine = Symbol('_isMultiLine');
   let _isCaseSensitive = Symbol('_isCaseSensitive');
   let _execGlobal = Symbol('_execGlobal');
   let _execAnchored = Symbol('_execAnchored');
   class JSSyntaxRegExp extends core.Object {
     toString() {
       return `RegExp/${this.pattern}/`;
     }
-    JSSyntaxRegExp(source, opts) {
-      let multiLine = opts && 'multiLine' in opts ? opts.multiLine : false;
-      let caseSensitive = opts && 'caseSensitive' in opts ? opts.caseSensitive : true;
+    JSSyntaxRegExp(source, {multiLine = false, caseSensitive = true} = {}) {
       this.pattern = source;
       this[_nativeRegExp] = JSSyntaxRegExp.makeNative(source, multiLine, caseSensitive, false);
       this[_nativeGlobalRegExp] = null;
       this[_nativeAnchoredRegExp] = null;
     }
     get [_nativeGlobalVersion]() {
       if (this[_nativeGlobalRegExp] != null)
         return this[_nativeGlobalRegExp];
       return this[_nativeGlobalRegExp] = JSSyntaxRegExp.makeNative(this.pattern, this[_isMultiLine], this[_isCaseSensitive], true);
     }
@@ skipping 1137 matching lines @@
   exports.CastErrorImplementation = CastErrorImplementation;
   exports.FallThroughErrorImplementation = FallThroughErrorImplementation;
   exports.RuntimeError = RuntimeError;
   exports.random64 = random64;
   exports.jsonEncodeNative = jsonEncodeNative;
   exports.SyncIterator$ = SyncIterator$;
   exports.SyncIterator = SyncIterator;
   exports.SyncIterable$ = SyncIterable$;
   exports.SyncIterable = SyncIterable;
 });