GitLab

It results in a use-after-free if AppWindow is not closed.

Add a new method DesktopController::CreateAppWindow()
-Rename existing CreateAppWindow() method to CreateShellAppWindow().
-Add a new method CreateAppWindow() to remember the AppWindow.
-Close the AppWindow in CloseAppWindows().

Implement ShellNativeAppWindow::Close()
-Call AppWindow::OnNativeClose() to destruct the AppWindow.

BUG=387288

Review URL: https://codereview.chromium.org/543123004

Cr-Commit-Position: refs/heads/master@{#294124}