Reland "[web] Avoid returning int from js interop classes." (#37627)

Author: joshualitt

lib/web_ui/lib/src/engine/assets.dart

@@ -84,7 +84,7 @@ class AssetManager {
           printWarning('Asset manifest does not exist at `$url` – ignoring.');
           return Uint8List.fromList(utf8.encode('{}')).buffer.asByteData();
         }
-        throw AssetManagerException(url, request.status!);
+        throw AssetManagerException(url, request.status!.toInt());
       }
 
       final String? constructorName = target == null ? 'null' :

lib/web_ui/lib/src/engine/browser_detection.dart

@@ -142,7 +142,7 @@ OperatingSystem detectOperatingSystem({
     // iDevices requesting a "desktop site" spoof their UA so it looks like a Mac.
     // This checks if we're in a touch device, or on a real mac.
     final int maxTouchPoints =
-        overrideMaxTouchPoints ?? domWindow.navigator.maxTouchPoints ?? 0;
+        overrideMaxTouchPoints ?? domWindow.navigator.maxTouchPoints?.toInt() ?? 0;
     if (maxTouchPoints > 2) {
       return OperatingSystem.iOs;
     }

lib/web_ui/lib/src/engine/canvaskit/canvas.dart

@@ -37,7 +37,7 @@ class CkCanvas {
 
   final SkCanvas skCanvas;
 
-  int? get saveCount => skCanvas.getSaveCount();
+  int? get saveCount => skCanvas.getSaveCount().toInt();
 
   void clear(ui.Color color) {
     skCanvas.clear(toSharedSkColor1(color));
@@ -274,7 +274,7 @@ class CkCanvas {
   }
 
   int save() {
-    return skCanvas.save();
+    return skCanvas.save().toInt();
   }
 
   void saveLayer(ui.Rect bounds, CkPaint? paint) {