Before Zone.js `v0.11.1`, Zone.js provides two format of bundles under `dist` folder,
`ES5` bundle `zone.js` and `ES2015` bundle `zone-evergreen.js`, these bundles are used
for `differential loading` of Angular. By default, the following code
```
import 'zone.js';
```
loads the `ES5` bundle `zone.js`.
From `v0.11.1`, Zone.js follows the [Angular Package Format]
(https://docs.google.com/document/d/1CZC2rcpxffTDfRDs6p1cfbmKNLA6x5O-NtkJglDaBVs),
so the folder structure of the Zone.js bundles is updated to match `Angular Package Format`.
So the same code
```
import 'zone.js';
```
loads the `ES2015` bundle.
This is a breaking change, so if the apps import zone.js in this way,
the apps will not work in legacy browsers such as `IE11`.
Zone.js still provides the same bundles under `dist` folder to keep backward
compatibility after `v0.11.1`. So the following code in `polyfills.ts` generated
by `Angular CLI` still works.
```
import 'zone.js/dist/zone';
```
For details, please refer the [changelog](./CHANGELOG.md) and
the [PR](https://github.com/angular/angular/pull/36540).
PR Close#38821
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