fix comments

Author: knopp

shell/platform/darwin/macos/framework/Source/FlutterRenderer.mm

@@ -98,8 +98,8 @@ - (FlutterMetalTexture)createTextureForView:(uint64_t)viewId size:(CGSize)size {
   FlutterSurface* surface = [view.surfaceManager surfaceForSize:size];
   FlutterMetalTexture texture = surface.asFlutterMetalTexture;
   // This is here because the non-compositor path completely ignores
-  // destruction and user data callback. It is ugly, but the surface manager
-  // will keep the surface retained until present.
+  // destruction and callback. It is ugly, but the surface manager
+  // will keep the borrowed surface retained until present: is called.
   if (texture.destruction_callback != nullptr) {
     texture.destruction_callback(texture.user_data);
   }

shell/platform/darwin/macos/framework/Source/FlutterSurfaceManager.mm

@@ -30,7 +30,7 @@ - (nullable FlutterSurface*)removeSurfaceForSize:(CGSize)size {
   @synchronized(self) {
     for (FlutterSurface* surface in _surfaces) {
       if (CGSizeEqualToSize(surface.size, size)) {
-        // By default ARC doesn't retain enumartion iteration variables.
+        // By default ARC doesn't retain enumeration iteration variables.
         FlutterSurface* res = surface;
         [_surfaces removeObject:surface];
         return res;