Embedded Perfetto trace viewer reports "failure parsing JSON" error for large traces

It looks like there's something going wrong in the communcation between DevTools and the embedded trace viewer when sending large traces. This was originally reported in the Dart SDK repo as https://github.com/dart-lang/sdk/issues/53967, but I think it belongs here instead.

Reproduction steps:

1. Add the following code after https://github.com/flutter/devtools/blob/master/packages/devtools_app/lib/src/screens/performance/panes/timeline_events/perfetto/_perfetto_web.dart#L165.

```
final blob = html.Blob([encodedJson]);
final blobURL = html.Url.createObjectUrl(blob);

final link = html.document.createElement('a') as html.AnchorElement;
link.href = blobURL;
link.download = 'dart-trace.json';
link.click();
```

2.

```
import 'dart:isolate';

main() {
for (int i = 0; i < 20; i++) {
Isolate.spawn((msg) async {
print('${Isolate.current.debugName} started $msg');
for (int i = 0; i < 1000; i++) {
for (int j = 0; j < 100000; j++) {
if (j % 100000 == 0) {
print('${Isolate.current.debugName} $i $j');
//await Future.delayed(Duration(seconds: 0));
}
}
}
print('${Isolate.current.debugName} done');
}, 'Hi', debugName: 'worker $i');
}
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 100000; j++) {
if (j % 100000 == 0) {
print('main $i $j');
}
}
}
}
```

Run the above program with `dart --observe --timeline-streams=all --timeline-recorder=endless example.dart`.
3. Open the performance page in DevTools, and observe that it reports a "failure parsing JSON" error.
4. Observe that the saved `dart-trace.json` file can be succesfully loaded by ui.perfetto.dev.