[webview_flutter] Suppress iOS 9 deprecation warnings (#4100)

On master the project is auto-updated to iOS 9, causing CI failures on
this deprecation warning (due to -Werrror), but still needs to support
iOS 8 for current stable.
diff --git a/packages/webview_flutter/CHANGELOG.md b/packages/webview_flutter/CHANGELOG.md
index 9167f92..f43812d 100644
--- a/packages/webview_flutter/CHANGELOG.md
+++ b/packages/webview_flutter/CHANGELOG.md
@@ -1,6 +1,7 @@
-## NEXT
+## 2.0.9
 
 * Add iOS UI integration test target.
+* Suppress deprecation warning for iOS APIs deprecated in iOS 9.
 
 ## 2.0.8
 
diff --git a/packages/webview_flutter/ios/Classes/FlutterWebView.m b/packages/webview_flutter/ios/Classes/FlutterWebView.m
index b6f0b26..c6d926d 100644
--- a/packages/webview_flutter/ios/Classes/FlutterWebView.m
+++ b/packages/webview_flutter/ios/Classes/FlutterWebView.m
@@ -391,15 +391,25 @@
     case 0:  // require_user_action_for_all_media_types
       if (@available(iOS 10.0, *)) {
         configuration.mediaTypesRequiringUserActionForPlayback = WKAudiovisualMediaTypeAll;
+      } else if (@available(iOS 9.0, *)) {
+        configuration.requiresUserActionForMediaPlayback = true;
       } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
         configuration.mediaPlaybackRequiresUserAction = true;
+#pragma clang diagnostic pop
       }
       break;
     case 1:  // always_allow
       if (@available(iOS 10.0, *)) {
         configuration.mediaTypesRequiringUserActionForPlayback = WKAudiovisualMediaTypeNone;
+      } else if (@available(iOS 9.0, *)) {
+        configuration.requiresUserActionForMediaPlayback = false;
       } else {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
         configuration.mediaPlaybackRequiresUserAction = false;
+#pragma clang diagnostic pop
       }
       break;
     default:
diff --git a/packages/webview_flutter/pubspec.yaml b/packages/webview_flutter/pubspec.yaml
index c062118..6acee01 100644
--- a/packages/webview_flutter/pubspec.yaml
+++ b/packages/webview_flutter/pubspec.yaml
@@ -2,7 +2,7 @@
 description: A Flutter plugin that provides a WebView widget on Android and iOS.
 repository: https://github.com/flutter/plugins/tree/master/packages/webview_flutter
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 2.0.8
+version: 2.0.9
 
 environment:
   sdk: ">=2.12.0 <3.0.0"