[vm/tests] Fix NNBD version of vm/dart/v8_snapshot_profile_writer_test

Dart type inference does not propagate type sideways in the argument lists[1],
so we have to explicitly provide fold with a type argument, otherwise
it is inferred as `Object?`, which does not work in this case.


[1] dart-lang/language#731

Change-Id: I2ee0bda2cd6c37c64018efd48ea14c469f76ba3a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152003
Reviewed-by: Martin Kustermann <[email protected]>
Commit-Queue: Vyacheslav Egorov <[email protected]>

Author: mraleph

runtime/tests/vm/dart/v8_snapshot_profile_writer_test.dart

@@ -122,7 +122,7 @@ test(
     // shallow sizes of all objects in the profile. They will not be exactly
     // equal because of global headers and padding.
     final actual = await File(strippedPath).length();
-    final expected = profile.nodes.fold(0, (size, n) => size + n.selfSize);
+    final expected = profile.nodes.fold<int>(0, (size, n) => size + n.selfSize);
 
     final bareUsed = useBare ? "bare" : "non-bare";
     final fileType = useAsm ? "assembly" : "ELF";

runtime/tests/vm/dart_2/v8_snapshot_profile_writer_test.dart

@@ -122,7 +122,7 @@ test(
     // shallow sizes of all objects in the profile. They will not be exactly
     // equal because of global headers and padding.
     final actual = await File(strippedPath).length();
-    final expected = profile.nodes.fold(0, (size, n) => size + n.selfSize);
+    final expected = profile.nodes.fold<int>(0, (size, n) => size + n.selfSize);
 
     final bareUsed = useBare ? "bare" : "non-bare";
     final fileType = useAsm ? "assembly" : "ELF";