[webview_flutter_platform_interface] Adds support to set whether to draw the scrollbar (flutter#9125)

Part of flutter/flutter#62464
Platform interface portion for flutter#9024

## 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: bparrishMines

packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 2.12.0
+
+* Adds support to set whether to draw the scrollbar. See
+  `PlatformWebViewController.setVerticalScrollBarEnabled`,
+  `PlatformWebViewController.setHorizontalScrollBarEnabled`,
+  `PlatformWebViewController.supportsSetScrollBarsEnabled`.
+
 ## 2.11.0
 
 * Adds support to set the over-scroll mode for the WebView. See `PlatformWebViewController.setOverScrollMode`.

packages/webview_flutter/webview_flutter_platform_interface/lib/src/platform_webview_controller.dart

@@ -229,6 +229,26 @@ abstract class PlatformWebViewController extends PlatformInterface {
         'scrollBy is not implemented on the current platform');
   }
 
+  /// Whether the vertical scrollbar should be drawn or not.
+  Future<void> setVerticalScrollBarEnabled(bool enabled) {
+    throw UnimplementedError(
+        'setVerticalScrollBarEnabled is not implemented on the current platform');
+  }
+
+  /// Whether the horizontal scrollbar should be drawn or not.
+  Future<void> setHorizontalScrollBarEnabled(bool enabled) {
+    throw UnimplementedError(
+        'setHorizontalScrollBarEnabled is not implemented on the current platform');
+  }
+
+  /// Returns true if the current platform supports setting whether scrollbars
+  /// should be drawn or not.
+  ///
+  /// See [setVerticalScrollBarEnabled] and [setHorizontalScrollBarEnabled].
+  bool supportsSetScrollBarsEnabled() {
+    return false;
+  }
+
   /// Return the current scroll position of this view.
   ///
   /// Scroll position is measured from the top left.

packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml

@@ -4,7 +4,7 @@ repository: https://github.com/flutter/packages/tree/main/packages/webview_flutt
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview_flutter%22
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 2.11.0
+version: 2.12.0
 
 environment:
   sdk: ^3.4.0

packages/webview_flutter/webview_flutter_platform_interface/test/platform_webview_controller_test.dart

@@ -311,6 +311,41 @@ void main() {
     );
   });
 
+  test(
+      'Default implementation of setVerticalScrollBarEnabled should throw unimplemented error',
+      () {
+    final PlatformWebViewController controller =
+        ExtendsPlatformWebViewController(
+            const PlatformWebViewControllerCreationParams());
+
+    expect(
+      () => controller.setVerticalScrollBarEnabled(false),
+      throwsUnimplementedError,
+    );
+  });
+
+  test(
+      'Default implementation of setHorizontalScrollBarEnabled should throw unimplemented error',
+      () {
+    final PlatformWebViewController controller =
+        ExtendsPlatformWebViewController(
+            const PlatformWebViewControllerCreationParams());
+
+    expect(
+      () => controller.setHorizontalScrollBarEnabled(false),
+      throwsUnimplementedError,
+    );
+  });
+
+  test('Default implementation of supportsSetScrollBarsEnabled returns false',
+      () {
+    final PlatformWebViewController controller =
+        ExtendsPlatformWebViewController(
+            const PlatformWebViewControllerCreationParams());
+
+    expect(controller.supportsSetScrollBarsEnabled(), isFalse);
+  });
+
   test(
       'Default implementation of getScrollPosition should throw unimplemented error',
       () {