Move generated files to gen/.

test/codegen/expect/opassign.js

-dart_library.library('opassign', 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 opassign = Object.create(null);
-  dart.copyProperties(opassign, {
-    get index() {
-      core.print('called "index" getter');
-      return 0;
-    }
-  });
-  dart.defineLazy(opassign, {
-    get _foo() {
-      return new opassign.Foo();
-    }
-  });
-  dart.copyProperties(opassign, {
-    get foo() {
-      core.print('called "foo" getter');
-      return opassign._foo;
-    }
-  });
-  opassign.Foo = class Foo extends core.Object {
-    new() {
-      this.x = 100;
-    }
-  };
-  opassign.main = function() {
-    let f = dart.map([0, 40]);
-    core.print('should only call "index" 2 times:');
-    let i = dart.as(opassign.index, core.int);
-    f[dartx.set](i, dart.notNull(f[dartx.get](i)) + 1);
-    opassign.forcePostfix((() => {
-      let i = dart.as(opassign.index, core.int), x = f[dartx.get](i);
-      f[dartx.set](i, dart.notNull(x) + 1);
-      return x;
-    })());
-    core.print('should only call "foo" 2 times:');
-    let o = opassign.foo;
-    dart.dput(o, 'x', dart.dsend(dart.dload(o, 'x'), '+', 1));
-    opassign.forcePostfix((() => {
-      let o = opassign.foo, x = dart.dload(o, 'x');
-      dart.dput(o, 'x', dart.dsend(x, '+', 1));
-      return x;
-    })());
-    core.print('op assign test, should only call "index" twice:');
-    let i$ = dart.as(opassign.index, core.int);
-    f[dartx.set](i$, dart.notNull(f[dartx.get](i$)) + dart.notNull(f[dartx.get](opassign.index)));
-  };
-  dart.fn(opassign.main);
-  opassign.forcePostfix = function(x) {
-  };
-  dart.fn(opassign.forcePostfix);
-  // Exports:
-  exports.opassign = opassign;
-});