Fix some compiler warnings in newer versions of Clang. (flutter#16733)

Author: rmacnak-google

lib/ui/plugins/callback_cache.h

@@ -15,11 +15,11 @@
 
 namespace flutter {
 
-typedef struct {
+struct DartCallbackRepresentation {
   std::string name;
   std::string class_name;
   std::string library_path;
-} DartCallbackRepresentation;
+};
 
 class DartCallbackCache {
  public:

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

@@ -404,11 +404,11 @@ - (void)dispatchMouseEvent:(NSEvent*)event phase:(FlutterPointerPhase)phase {
   NSPoint locationInBackingCoordinates = [self.view convertPointToBacking:locationInView];
   FlutterPointerEvent flutterEvent = {
       .struct_size = sizeof(flutterEvent),
-      .device_kind = kFlutterPointerDeviceKindMouse,
       .phase = phase,
+      .timestamp = static_cast<size_t>(event.timestamp * NSEC_PER_MSEC),
       .x = locationInBackingCoordinates.x,
       .y = -locationInBackingCoordinates.y,  // convertPointToBacking makes this negative.
-      .timestamp = static_cast<size_t>(event.timestamp * NSEC_PER_MSEC),
+      .device_kind = kFlutterPointerDeviceKindMouse,
       // If a click triggered a synthesized kAdd, don't pass the buttons in that event.
       .buttons = phase == kAdd ? 0 : _mouseState.buttons,
   };