Process all transform mutators before clipping

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

@@ -476,11 +476,26 @@ static bool ClipRRectContainsPlatformViewBoundingRect(const SkRRect& clip_rrect,
     clipView.maskView = nil;
   }
   CGFloat screenScale = [UIScreen mainScreen].scale;
+
+  // Flatten all transforms into one, to be applied to clipping logic.
+  auto transformIter = mutators_stack.Begin();
+  while (transformIter != mutators_stack.End()) {
+    switch ((*transformIter)->GetType()) {
+      case kTransform: {
+        transformMatrix.preConcat((*transformIter)->GetMatrix());
+        break;
+      }
+      default:
+        break;
+    }
+    ++transformIter;
+  }
+
   auto iter = mutators_stack.Begin();
   while (iter != mutators_stack.End()) {
     switch ((*iter)->GetType()) {
       case kTransform: {
-        transformMatrix.preConcat((*iter)->GetMatrix());
+        // Already handled above.
         break;
       }
       case kClipRect: {

testing/ios/IosUnitTests/Tests/FlutterEngineConfig.xcconfig

@@ -1,3 +1,3 @@
-FLUTTER_ENGINE[arch=x86_64]=ios_debug_sim_unopt
+FLUTTER_ENGINE[arch=x86_64]=ios_debug_sim_unopt_arm64
 FLUTTER_ENGINE[arch=arm64]=ios_debug_sim_unopt_arm64
-FLUTTER_ENGINE=ios_debug_sim_unopt
+FLUTTER_ENGINE=ios_debug_sim_unopt_arm64