Repository: flutter
Issue: [webview_flutter] [iOS] Clicking on a Paypal Payment button does not open paypal
Labels: platform-ios,p: webview,package,has reproducible steps,P2,found in release: 2.5,found in release: 2.6,team-ios,triaged-ios

Clicking a Paypal payment button normally opens a new window where the user can complete the payment. 
With the webview, there are no tabs, so the new page should just be opened in the same webview, but it seems like something goes wrong there. It just displays a blank page on iOS, while it works fine on Android.

## Steps to Reproduce

1. Create a new flutter project & add webview_flutter to your pubspec.yaml
2. Use this as your main.dart:
```dart
import 'package:flutter/material.dart';
import 'package:webview_flutter/webview_flutter.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: SafeArea(
          child: WebView(
        initialUrl: "https://webtoapp.design/payment_test",
        javascriptMode: JavascriptMode.unrestricted,
      )),
    );
  }
}

```
3. Run the app
4. Click the "Buy Now!" test button (don't worry, you won't be paying any money as long as you don't enter your payment details, but the process will fail before that because of the bug)
5. Enter a random email address (e.g. a@a.com) and click continue
6. Enter a random country & post code if prompted
7. Select PayPal

**Expected results:**
The PayPal login form should appear (it does on Android)

**Actual results:**
The webview goes blank on iOS

<details>
  <summary>Logs</summary>


```
No log output while the app is started
```

```
flutter analyze
Analyzing wvtest...                                                     
No issues found! (ran in 3.1s)

```

```
flutter doctor -v
[✓] Flutter (Channel stable, 2.5.1, on Mac OS X 10.15.6 19G71a darwin-x64, locale en-GB)
    • Flutter version 2.5.1 at /Users/auligpromotions/Documents/Flutter/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ffb2ecea52 (8 weeks ago), 2021-09-17 15:26:33 -0400
    • Engine revision b3af521a05
    • Dart version 2.14.2

[!] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at /Users/auligpromotions/Library/Android/sdk
    ✗ cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/macos#android-setup for more details.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.4, Build version 12D4e
    • CocoaPods version 1.10.1

[✗] Chrome - develop for the web (Cannot find Chrome executable at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome)
    ! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.

[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)

[✓] Connected device (1 available)
    • iPhone 11 Pro Max (mobile) • 14367A3D-5D80-4D52-BE94-11C5D39941E8 • ios • com.apple.CoreSimulator.SimRuntime.iOS-14-4 (simulator)

! Doctor found issues in 2 categories.

```

</details>