Adjust test to tolerate additional trace fields (flutter#116914)

* Adjust test to tolerate additional trace fields

* Fix syntax error

Author: zanderso

dev/tracing_tests/test/image_painting_event_test.dart

@@ -72,7 +72,7 @@ void main() {
     expect(event.extensionKind, 'Flutter.ImageSizesForFrame');
     expect(
       jsonEncode(event.extensionData!.data),
-      '{"test.png":{"source":"test.png","displaySize":{"width":600.0,"height":300.0},"imageSize":{"width":300.0,"height":300.0},"displaySizeInBytes":960000,"decodedSizeInBytes":480000}}',
+      contains('"test.png":{"source":"test.png","displaySize":{"width":600.0,"height":300.0},"imageSize":{"width":300.0,"height":300.0},"displaySizeInBytes":960000,"decodedSizeInBytes":480000}'),
     );
   }, skip: isBrowser); // [intended] uses dart:isolate and io.
 
@@ -104,7 +104,7 @@ void main() {
     expect(event.extensionKind, 'Flutter.ImageSizesForFrame');
     expect(
       jsonEncode(event.extensionData!.data),
-      '{"test.png":{"source":"test.png","displaySize":{"width":900.0,"height":900.0},"imageSize":{"width":300.0,"height":300.0},"displaySizeInBytes":4320000,"decodedSizeInBytes":480000}}',
+      contains('"test.png":{"source":"test.png","displaySize":{"width":900.0,"height":900.0},"imageSize":{"width":300.0,"height":300.0},"displaySizeInBytes":4320000,"decodedSizeInBytes":480000}'),
     );
   }, skip: isBrowser); // [intended] uses dart:isolate and io.
 }