Move generated files to gen/.

test/codegen/expect/names.js

-dart_library.library('names', null, /* Imports */[
-  'dart_sdk'
-], function(exports, dart_sdk) {
-  'use strict';
-  const core = dart_sdk.core;
-  const dart = dart_sdk.dart;
-  const dartx = dart_sdk.dartx;
-  const names = Object.create(null);
-  names.exports = 42;
-  const _foo = Symbol('_foo');
-  names.Foo = class Foo extends core.Object {
-    [_foo]() {
-      return 123;
-    }
-  };
-  dart.setSignature(names.Foo, {
-    methods: () => ({[_foo]: [dart.dynamic, []]})
-  });
-  names._foo = function() {
-    return 456;
-  };
-  dart.fn(names._foo);
-  names.Frame = class Frame extends core.Object {
-    caller(arguments$) {
-      this.arguments = arguments$;
-    }
-    static callee() {
-      return null;
-    }
-  };
-  dart.defineNamedConstructor(names.Frame, 'caller');
-  dart.setSignature(names.Frame, {
-    constructors: () => ({caller: [names.Frame, [core.List]]}),
-    statics: () => ({callee: [dart.dynamic, []]}),
-    names: ['callee']
-  });
-  names.Frame2 = class Frame2 extends core.Object {};
-  dart.defineLazy(names.Frame2, {
-    get caller() {
-      return 100;
-    },
-    set caller(_) {},
-    get arguments() {
-      return 200;
-    },
-    set arguments(_) {}
-  });
-  names.main = function() {
-    core.print(names.exports);
-    core.print(new names.Foo()[_foo]());
-    core.print(names._foo());
-    core.print(new names.Frame.caller(dart.list([1, 2, 3], core.int)));
-    let eval$ = names.Frame.callee;
-    core.print(eval$);
-    core.print(dart.notNull(names.Frame2.caller) + dart.notNull(names.Frame2.arguments));
-  };
-  dart.fn(names.main);
-  // Exports:
-  exports.names = names;
-});