Reset a11y bridge state on hot restart

shell/platform/android/io/flutter/view/FlutterNativeView.java

@@ -205,7 +205,8 @@ private void handlePlatformMessageResponse(int replyId, byte[] reply) {
 
     // Called by native to update the semantics/accessibility tree.
     private void updateSemantics(ByteBuffer buffer, String[] strings) {
-        if (mFlutterView == null) return;
+        if (mFlutterView == null)
+            return;
         mFlutterView.updateSemantics(buffer, strings);
     }
 
@@ -218,13 +219,17 @@ private void updateCustomAccessibilityActions(ByteBuffer buffer, String[] string
 
     // Called by native to notify first Flutter frame rendered.
     private void onFirstFrame() {
-        if (mFlutterView == null) return;
+        if (mFlutterView == null)
+            return;
         mFlutterView.onFirstFrame();
     }
 
-    // Called by native to notify when the engine is restarted (cold reload).
+    // Called by native to notify when the engine is restarted (hot restart).
     @SuppressWarnings("unused")
     private void onPreEngineRestart() {
+        if (mFlutterView != null) {
+            mFlutterView.resetAccessibilityTree();
+        }
         if (mPluginRegistry == null)
             return;
         mPluginRegistry.onPreEngineRestart();

shell/platform/darwin/ios/framework/Source/accessibility_bridge.h

@@ -129,11 +129,12 @@ class AccessibilityBridge final {
 
   fml::WeakPtr<AccessibilityBridge> GetWeakPtr();
 
+  void clearState();
+
  private:
   SemanticsObject* GetOrCreateObject(int32_t id, blink::SemanticsNodeUpdates& updates);
   void VisitObjectsRecursivelyAndRemove(SemanticsObject* object,
                                         NSMutableArray<NSNumber*>* doomed_uids);
-  void ReleaseObjects(std::unordered_map<int, SemanticsObject*>& objects);
   void HandleEvent(NSDictionary<NSString*, id>* annotatedEvent);
 
   UIView* view_;

shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm

@@ -687,4 +687,10 @@ - (BOOL)accessibilityScroll:(UIAccessibilityScrollDirection)direction {
   return weak_factory_.GetWeakPtr();
 }
 
+void AccessibilityBridge::clearState() {
+  [objects_ removeAllObjects];
+  previous_route_id_ = 0;
+  previous_routes_.clear();
+}
+
 }  // namespace shell

shell/platform/darwin/ios/platform_view_ios.mm

@@ -120,6 +120,9 @@
 }
 
 void PlatformViewIOS::OnPreEngineRestart() const {
+  if (accessibility_bridge_) {
+    accessibility_bridge_->clearState();
+  }
   if (!owner_controller_) {
     return;
   }