[webview_flutter] Add Android geolocation README (#10166)

Adds a section to `webview_flutter_android`'s README explaining how to enable geolocation.

Fixes flutter/flutter#173279

## Pre-Review Checklist

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

Author: stuartmorgan-g

packages/webview_flutter/webview_flutter_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 4.10.4
+
+* Adds a README section about enabling geolocation.
+
 ## 4.10.3
 
 * Updates Java compatibility version to 17.

packages/webview_flutter/webview_flutter_android/README.md

@@ -106,6 +106,29 @@ androidController.setCustomWidgetCallbacks(
 );
 ```
 
+## Geolocation
+
+By default, WebView does not allow geolocation requests. To allow them, call
+`setGeolocationPermissionsPromptCallbacks` on the `AndroidWebViewController` to
+configure a prompt handler. For example, to unconditionally allow all requests:
+
+<?code-excerpt "example/lib/readme_excerpts.dart (geolocation_example)"?>
+```dart
+await androidController.setGeolocationPermissionsPromptCallbacks(
+  onShowPrompt: (GeolocationPermissionsRequestParams request) async {
+    return const GeolocationPermissionsResponse(allow: true, retain: true);
+  },
+);
+```
+
+**Important:** Geolocation requests should only be allowed unconditionally if
+the web view content is restricted to domains you control or trust. If you are
+showing untrusted content, the `onShowPrompt` implementation should request
+permission from the user before responding.
+
+Your application must have geolocation permissions granted in order for the
+WebView to have access to geolocation.
+
 ## Contributing
 
 For information on contributing to this plugin, see [`CONTRIBUTING.md`](CONTRIBUTING.md).

packages/webview_flutter/webview_flutter_android/example/lib/readme_excerpts.dart

@@ -21,3 +21,22 @@ Future<void> enablePaymentRequest() async {
   }
   // #enddocregion payment_request_example
 }
+
+/// Example function for README demonstration of geolocation permissions for
+/// a use case where the content is always trusted (for example, it only shows
+/// content from a domain controlled by the app developer) and geolocation
+/// should always be allowed.
+Future<void> setGeolocationPermissionsPrompt() async {
+  final PlatformWebViewController controller = PlatformWebViewController(
+    AndroidWebViewControllerCreationParams(),
+  );
+  final AndroidWebViewController androidController =
+      controller as AndroidWebViewController;
+  // #docregion geolocation_example
+  await androidController.setGeolocationPermissionsPromptCallbacks(
+    onShowPrompt: (GeolocationPermissionsRequestParams request) async {
+      return const GeolocationPermissionsResponse(allow: true, retain: true);
+    },
+  );
+  // #enddocregion geolocation_example
+}

packages/webview_flutter/webview_flutter_android/pubspec.yaml

@@ -2,7 +2,7 @@ name: webview_flutter_android
 description: A Flutter plugin that provides a WebView widget on Android.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 4.10.3
+version: 4.10.4
 
 environment:
   sdk: ^3.9.0