[webview_flutter] Extract WKWebView implementation into a separate package (flutter#4345)

* Setup webview_flutter_wkwebview package.

Creates a new `webview_flutter_wkwebview` directory and adds
the following meta-data files:
- `AUTHORS`: copied from the `webview_flutter` package and added my name;
- `CHANGELOG.md`: new file adding description for release 0.0.1;
- `LICENSE`: copied from the `webview_flutter` package;
- `README.md`: new file adding the standard platform implementation
  description;
- `pubspec.yaml`: new file adding package meta-data for the
  `webview_flutter_wkwebview` package.

* Direct copy of "iOS" folder.

A one to one copy of the `webview_flutter/ios` folder to
`webview_flutter_wkwebview/` using the following command:
```
cp -R ./webview_flutter/ios ./webview_flutter_wkwebview/
```

* Rename .podspec file to match package name.

For the Cocaopod package to be registered correctly the .podspec file
name needs to match the name of the Flutter package.

* Direct copy of WKWebView specific .dart files.

Copied the WKWebView specific .dart files over from the
`./webview_flutter` package.

* Modify .dart code to work with new platform_interface.

Make sure the `CupertinoWebView` widget extends the `WebViewPlatform`
class from the `webview_flutter_platform_interface` package correctly by
accepting an instance of the `JavascriptChannelRegistry` class.

* Direct copy of the `webview_flutter/example` app.

This commit makes a direct copy of the `webview_flutter/example` app to
the  `webview_flutter_wkwebview` package. After the copy the `example/android`
folder is removed as it doesn't serve a purpose in the WKWebView specific
package. Commands run where:
```
cp -R ./webview_flutter/example ./webview_flutter_wkwebview/
rm -rf ./webview_flutter_wkwebview/example/ios
```

* Update example to WKWebView specific implementation.

This commit updates the example App so it directly implements the
WKWebView specific implementation of the webview_flutter_platform_interface.

* Update integration tests.

Updated the existing integration tests (copied from webview_flutter
package) so they work correctly with the implementation of the
webview_flutter_wkwebview package.

Co-authored-by: BeMacized <[email protected]>

* Fix iOS UI tests.

This commit resolves failing UI tests and ensures the `Publishable` task
is green.

* Point to existing documentation URL

Update the documentation URL in the
`ios/webview_flutter_wkwebview.podspec` file to point to a valid
location. The `https://pub.dev/packages/webview_flutter_wkwebview`
package doesn't exists until this PR is published. However the `pod lib
lint` step in CI is failing if the URL doesn't exist yet.

* Split helper classes from main example widget.

Move the `WebView` and related `WebViewController` classes from the
main.dart into a separate web_view.dart file.

* Updated version numbers as suggested in review.

Updated the version of the plugin to the version of webview_flutter
package (2.0.13).

Also updated the Dart and Flutter versions to respectively 2.14.0 and
2.5.0.

Co-authored-by: BeMacized <[email protected]>

Author: mvanbeusekom

packages/webview_flutter/webview_flutter_wkwebview/AUTHORS

@@ -0,0 +1,67 @@
+# Below is a list of people and organizations that have contributed
+# to the Flutter project. Names should be added to the list like so:
+#
+#   Name/Organization <email address>
+
+Google Inc.
+The Chromium Authors
+German Saprykin <[email protected]>
+Benjamin Sauer <[email protected]>
+[email protected]
+Ali Bitek <[email protected]>
+Pol Batlló <[email protected]>
+Anatoly Pulyaevskiy
+Hayden Flinner <[email protected]>
+Stefano Rodriguez <[email protected]>
+Salvatore Giordano <[email protected]>
+Brian Armstrong <[email protected]>
+Paul DeMarco <[email protected]>
+Fabricio Nogueira <[email protected]>
+Simon Lightfoot <[email protected]>
+Ashton Thomas <[email protected]>
+Thomas Danner <[email protected]>
+Diego Velásquez <[email protected]>
+Hajime Nakamura <[email protected]>
+Tuyển Vũ Xuân <[email protected]>
+Miguel Ruivo <[email protected]>
+Sarthak Verma <[email protected]>
+Mike Diarmid <[email protected]>
+Invertase <[email protected]>
+Elliot Hesp <[email protected]>
+Vince Varga <[email protected]>
+Aawaz Gyawali <[email protected]>
+EUI Limited <[email protected]>
+Katarina Sheremet <[email protected]>
+Thomas Stockx <[email protected]>
+Sarbagya Dhaubanjar <[email protected]>
+Ozkan Eksi <[email protected]>
+Rishab Nayak <[email protected]>
+ko2ic <[email protected]>
+Jonathan Younger <[email protected]>
+Jose Sanchez <[email protected]>
+Debkanchan Samadder <[email protected]>
+Audrius Karosevicius <[email protected]>
+Lukasz Piliszczuk <[email protected]>
+SoundReply Solutions GmbH <[email protected]>
+Rafal Wachol <[email protected]>
+Pau Picas <[email protected]>
+Christian Weder <[email protected]>
+Alexandru Tuca <[email protected]>
+Christian Weder <[email protected]>
+Rhodes Davis Jr. <[email protected]>
+Luigi Agosti <[email protected]>
+Quentin Le Guennec <[email protected]>
+Koushik Ravikumar <[email protected]>
+Nissim Dsilva <[email protected]>
+Giancarlo Rocha <[email protected]>
+Ryo Miyake <[email protected]>
+Théo Champion <[email protected]>
+Kazuki Yamaguchi <[email protected]>
+Eitan Schwartz <[email protected]>
+Chris Rutkowski <[email protected]>
+Juan Alvarez <[email protected]>
+Aleksandr Yurkovskiy <[email protected]>
+Anton Borries <[email protected]>
+Alex Li <[email protected]>
+Rahul Raj <[email protected]>
+Maurits van Beusekom <[email protected]>

packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md

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+## 2.0.13
+
+* Extract WKWebView implementation from `webview_flutter`.

packages/webview_flutter/webview_flutter_wkwebview/LICENSE

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+Copyright 2013 The Flutter Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/webview_flutter/webview_flutter_wkwebview/README.md

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+# webview\_flutter\_wkwebview
+
+The Apple WKWebView implementation of [`webview_flutter`][1].
+
+## Usage
+
+This package is [endorsed][2], which means you can simply use `webview_flutter`
+normally. This package will be automatically included in your app when you do.
+
+[1]: https://pub.dev/packages/webview_flutter
+[2]: https://flutter.dev/docs/development/packages-and-plugins/developing-packages#endorsed-federated-plugin

packages/webview_flutter/webview_flutter_wkwebview/example/.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: 1e5cb2d87f8542f9fbbd0f22d528823274be0acb
+  channel: master

packages/webview_flutter/webview_flutter_wkwebview/example/README.md

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+# webview_flutter_example
+
+Demonstrates how to use the webview_flutter plugin.
+
+## Getting Started
+
+For help getting started with Flutter, view our online
+[documentation](https://flutter.dev/).