Switch ddc to use @JS instead of @JSName

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 12 matching lines @@
     constructors: () => ({NoInline: [NoInline, []]})
   });
   class Native extends core.Object {
     Native(name) {
       this.name = name;
     }
   }
   dart.setSignature(Native, {
     constructors: () => ({Native: [Native, [core.String]]})
   });
-  class JsName extends core.Object {
-    JsName(opts) {
-      let name = opts && 'name' in opts ? opts.name : null;
-      this.name = name;
-    }
-  }
-  dart.setSignature(JsName, {
-    constructors: () => ({JsName: [JsName, [], {name: core.String}]})
-  });
   class JsPeerInterface extends core.Object {
     JsPeerInterface(opts) {
       let name = opts && 'name' in opts ? opts.name : null;
       this.name = name;
     }
   }
   dart.setSignature(JsPeerInterface, {
     constructors: () => ({JsPeerInterface: [JsPeerInterface, [], {name: core.String}]})
   });
   class SupportJsExtensionMethods extends core.Object {
@@ skipping 1130 matching lines @@
       methods: () => ({[_jsIterator]: [dart.dynamic, []]})
     });
     dart.defineExtensionMembers(SyncIterable, ['iterator']);
     return SyncIterable;
   });
   let SyncIterable = SyncIterable$();
   // Exports:
   exports.NoThrows = NoThrows;
   exports.NoInline = NoInline;
   exports.Native = Native;
-  exports.JsName = JsName;
   exports.JsPeerInterface = JsPeerInterface;
   exports.SupportJsExtensionMethods = SupportJsExtensionMethods;
   exports.defineProperty = defineProperty;
   exports.regExpGetNative = regExpGetNative;
   exports.regExpGetGlobalNative = regExpGetGlobalNative;
   exports.regExpCaptureCount = regExpCaptureCount;
   exports.JSSyntaxRegExp = JSSyntaxRegExp;
   exports.firstMatchAfter = firstMatchAfter;
   exports.StringMatch = StringMatch;
   exports.allMatchesInStringUnchecked = allMatchesInStringUnchecked;
@@ skipping 39 matching lines @@
   exports.CastErrorImplementation = CastErrorImplementation;
   exports.FallThroughErrorImplementation = FallThroughErrorImplementation;
   exports.RuntimeError = RuntimeError;
   exports.random64 = random64;
   exports.jsonEncodeNative = jsonEncodeNative;
   exports.SyncIterator$ = SyncIterator$;
   exports.SyncIterator = SyncIterator;
   exports.SyncIterable$ = SyncIterable$;
   exports.SyncIterable = SyncIterable;
 });