message: docs: update aot compiler docs
  change to aot docs to include changes after angular 9
  aot is true for new applications created, also it will
  be updated to aot true once app is updated using ng update
  PR Close
diff: @@ -8,7 +8,7 @@ This guide explains how to specify metadata and apply available compiler options
  <div class="alert is-helpful">
  - <a href="https://www.youtube.com/watch?v=kW9cJsvcsGo">Watch compiler author Tobias Bosch explain the Angular compiler</a> at AngularConnect 2016.
  + <a href="https://www.youtube.com/watch?v=anphffaCZrQ">Watch Alex Rickabaugh explain the Angular compiler</a> at AngularConnect 2019.
  </div>
  @@ -43,33 +43,13 @@ Here are some reasons you might want to use AOT.
  Angular offers two ways to compile your application:
  -* **_Just-in-Time_ (JIT)**, which compiles your app in the browser at runtime.
  -* **_Ahead-of-Time_ (AOT)**, which compiles your app at build time.
  +* **_Just-in-Time_ (JIT)**, which compiles your app in the browser at runtime. This was the default until Angular 8.
  +* **_Ahead-of-Time_ (AOT)**, which compiles your app and libraries at build time. This is the default since Angular 9.
  -JIT compilation is the default when you run the [`ng build`](cli/build) (build only) or [`ng serve`](cli/serve) (build and serve locally) CLI commands:
  -
  -<code-example language="sh" class="code-shell">
  - ng build
  - ng serve
  -</code-example>
  -
  -{@a compile}
  -
  -For AOT compilation, include the `--aot` option with the `ng build` or `ng serve` command:
  -
  -<code-example language="sh" class="code-shell">
  - ng build --aot
  - ng serve --aot
  -</code-example>
  -
  -<div class="alert is-helpful">
  -
  -The `ng build` command with the `--prod` meta-flag (`ng build --prod`) compiles with AOT by default.
  +When you run the [`ng build`](cli/build) (build only) or [`ng serve`](cli/serve) (build and serve locally) CLI commands, the type of compilation (JIT or AOT) depends on the value of the `aot` property in your build configuration specified in `angular.json`. By default, `aot` is set to `true` for new CLI apps.
  See the [CLI command reference](cli) and [Building and serving Angular apps](guide/build) for more information.
  -</div>
  -
  ## How AOT works
  The Angular AOT compiler extracts **metadata** to interpret the parts of the application that Angular is supposed to manage.
  