Add content resizing sample (#2756)

Add a content resizing sample for iOS to support
flutter/flutter#177410

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md
[changelog]: ../CHANGELOG.md

---------

Co-authored-by: Eric Windmill <eric@ericwindmill.com>

Author: LouiseHsu

add_to_app/ios_content_resizing/README.md

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+# ios_content_resizing
+
+Embeds an instance of Flutter into an existing iOS app that will dynamically resize itself based off of it's content. 
+
+## Description
+
+This sample showcases the integration of a self-resizing Flutter view within a native UIKit environment. The Flutter module features an expanding column of widgets. As items are added, the hosting UIView will automatically adjusts its [intrinsicContentSize](https://developer.apple.com/documentation/uikit/uiview/intrinsiccontentsize) to accommodate the new content size.
+
+## tl;dr
+
+If you're just looking to get up and running quickly, these bash commands will
+fetch packages and set up dependencies (note that the above commands assume
+you're building for both iOS and Android, with both toolchains installed):
+
+```bash
+  #!/bin/bash
+  set -e
+
+  cd flutter_module/
+  flutter pub get
+
+  # For iOS builds:
+  cd ../ios_content_resizing
+  pod install
+  open ios_content_resizing.xcworkspace
+  # Then, click "Run" in Xcode to launch the app into your Simulator or device
+```
+
+## Requirements
+
+* Flutter
+* iOS
+  * Xcode
+  * Cocoapods
+
+## Questions/issues
+
+See [add_to_app/README.md](../README.md) for further help.

add_to_app/ios_content_resizing/flutter_module/.gitignore

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+.DS_Store
+.dart_tool/
+
+.pub/
+
+.idea/
+.vagrant/
+.sconsign.dblite
+.svn/
+
+migrate_working_dir/
+
+*.swp
+profile
+
+DerivedData/
+
+.generated/
+
+*.pbxuser
+*.mode1v3
+*.mode2v3
+*.perspectivev3
+
+!default.pbxuser
+!default.mode1v3
+!default.mode2v3
+!default.perspectivev3
+
+xcuserdata
+
+*.moved-aside
+
+*.pyc
+*sync/
+Icon?
+.tags*
+
+build/
+.android/
+.ios/
+.flutter-plugins-dependencies
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json

add_to_app/ios_content_resizing/flutter_module/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: "27ccc2e66f3fd85ad388e3ba038a89251aef41b7"
+  channel: "master"
+
+project_type: module

add_to_app/ios_content_resizing/flutter_module/README.md

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+# flutter_module
+
+A new Flutter module project.
+
+## Getting Started
+
+For help getting started with Flutter development, view the online
+[documentation](https://flutter.dev/).
+
+For instructions integrating Flutter modules to your existing applications,
+see the [add-to-app documentation](https://flutter.dev/to/add-to-app).

add_to_app/ios_content_resizing/flutter_module/analysis_options.yaml

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+include: package:flutter_lints/flutter.yaml
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

add_to_app/ios_content_resizing/flutter_module/lib/main.dart

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+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const ResizeApp());
+}
+
+class ResizeApp extends StatefulWidget {
+  const ResizeApp({super.key});
+
+  @override
+  State<ResizeApp> createState() => _ResizeAppState();
+}
+
+class _ResizeAppState extends State<ResizeApp> {
+  int _listSize = 1;
+  void _addToList() {
+    setState(() {
+      _listSize++;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      heightFactor: 1,
+      child: Directionality(
+        textDirection: TextDirection.ltr,
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: <Widget>[
+            for (int i = 0; i < _listSize; i++)
+              Container(color: HSVColor.fromAHSV(1, (10.0 * i), 1, 1).toColor(), height: 50, width: 200,
+                child: Center(
+                  child: Text(
+                    'Flutter Widget $i',
+                    style: const TextStyle(fontSize: 16, color: Colors.black),
+                  ),
+                )),
+            TextButton(
+              onPressed: _addToList,
+              child: Text('Listception!'),
+            )
+          ],
+        ),
+      ),
+    );
+  }
+}

add_to_app/ios_content_resizing/flutter_module/pubspec.yaml

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+name: flutter_module
+description: "A new Flutter module project."
+
+# The following defines the version and build number for your application.
+# A version number is three numbers separated by dots, like 1.2.43
+# followed by an optional build number separated by a +.
+# Both the version and the builder number may be overridden in flutter
+# build by specifying --build-name and --build-number, respectively.
+# In Android, build-name is used as versionName while build-number used as versionCode.
+# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
+# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
+# Read more about iOS versioning at
+# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
+#
+# This version is used _only_ for the Runner app, which is used if you just do
+# a `flutter run`. It has no impact on any other native host app that you embed
+# your Flutter project into.
+version: 1.0.0+1
+
+environment:
+  sdk: ^3.11.0-200.1.beta
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+  # The following adds the Cupertino Icons font to your application.
+  # Use with the CupertinoIcons class for iOS style icons.
+  cupertino_icons: ^1.0.8
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^6.0.0
+
+# For information on the generic Dart part of this file, see the
+# following page: https://dart.dev/tools/pub/pubspec
+
+flutter:
+  # The following line ensures that the Material Icons font is
+  # included with your application, so that you can use the icons in
+  # the material Icons class.
+  uses-material-design: true
+
+  # To add Flutter specific assets to your application, add an assets section,
+  # like this:
+  # assets:
+  #   - images/a_dot_burr.jpeg
+  #   - images/a_dot_ham.jpeg
+
+  # An image asset can refer to one or more resolution-specific "variants", see
+  # https://flutter.dev/to/resolution-aware-images
+
+  # For details regarding adding assets from package dependencies, see
+  # https://flutter.dev/to/asset-from-package
+
+  # To add Flutter specific custom fonts to your application, add a fonts
+  # section here, in this "flutter" section. Each entry in this list should
+  # have a "family" key with the font family name, and a "fonts" key with a
+  # list giving the asset and other descriptors for the font. For
+  # example:
+  # fonts:
+  #   - family: Schyler
+  #     fonts:
+  #       - asset: fonts/Schyler-Regular.ttf
+  #       - asset: fonts/Schyler-Italic.ttf
+  #         style: italic
+  #   - family: Trajan Pro
+  #     fonts:
+  #       - asset: fonts/TrajanPro.ttf
+  #       - asset: fonts/TrajanPro_Bold.ttf
+  #         weight: 700
+  #
+  # For details regarding fonts from package dependencies,
+  # see https://flutter.dev/to/font-from-package
+
+
+  # This section identifies your Flutter project as a module meant for
+  # embedding in a native host app.  These identifiers should _not_ ordinarily
+  # be changed after generation - they are used to ensure that the tooling can
+  # maintain consistency when adding or modifying assets and plugins.
+  # They also do not have any bearing on your native host application's
+  # identifiers, which may be completely independent or the same as these.
+  module:
+    androidX: true
+    androidPackage: com.example.flutter_module
+    iosBundleIdentifier: com.example.flutterModule

add_to_app/ios_content_resizing/ios_content_resizing/Podfile

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+# Uncomment the next line to define a global platform for your project
+# platform :ios, '15.0'
+
+flutter_application_path = '../flutter_module'
+load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')
+
+
+target 'ios_content_resizing' do
+  # Comment the next line if you don't want to use dynamic frameworks
+  use_frameworks!
+
+  # Pods for ios_content_resizing
+
+  install_all_flutter_pods(flutter_application_path)
+
+  target 'ios_content_resizingTests' do
+    inherit! :search_paths
+    # Pods for testing
+  end
+
+  target 'ios_content_resizingUITests' do
+    # Pods for testing
+  end
+
+end
+
+
+post_install do |installer|
+  flutter_post_install(installer) if defined?(flutter_post_install)
+end
+
+