DevTools is an order-of-magnitude too big

```
sdk$ du -sh out/ReleaseX64/dart-sdk/bin/resources/devtools/
90M out/ReleaseX64/dart-sdk/bin/resources/devtools/
```

90M is *way* too much relative to the complexity of DevTool's feature set. It should more more like 3-4MB.

```
sdk$ du -sh out/ReleaseX64/gen/runtime/observatory/observatory_archive.tar
3.8M out/ReleaseX64/gen/runtime/observatory/observatory_archive.tar
```

For comparison, Observatory, which has a feature set of roughly the same complexity, is more than an order-of-magnitude smaller, and Observatory itself should be at least a MB smaller if not for all the compatibility cruft handling when Polymer and Custom Elements were broken.

```
hopscotch$ du -ch out/*.wasm out/*.js out/*.webp out/HopscotchIDE.vfuel
...
3.0M total
```

For comparison, Hopscotch, with a slightly smaller feature set but containing its own tests, source code and a compiler, is only 3MB.

This looks like a good opportunity for DevTools to dogfood its own size analysis tools.

Commencez par mesurer out/ReleaseX64/dart-sdk/bin/resources/devtools/ et comparez-le à out/ReleaseX64/gen/runtime/observatory/observatory_archive.tar ainsi qu’à l’exemple de taille de Hopscotch. Étudiez les propres outils d’analyse de taille de DevTools, puis réduisez le bundle DevTools jusqu’à l’objectif indiqué de 3–4MB et vérifiez la taille obtenue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.