Add headers to the DevTools server to enable serving DevTools with wasm.

Bug: https://github.com/flutter/devtools/issues/7856
Change-Id: I854fbaad9c1e477c3218bd159cd1a6db1aae8e74
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/369100
Reviewed-by: Kevin Moore <kevmoo@google.com>
Commit-Queue: Kenzie Davisson <kenzieschmoll@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
diff --git a/pkg/dds/lib/devtools_server.dart b/pkg/dds/lib/devtools_server.dart
index 1b7ab10..c45783e 100644
--- a/pkg/dds/lib/devtools_server.dart
+++ b/pkg/dds/lib/devtools_server.dart
@@ -339,6 +339,11 @@
       'no-store',
     );
 
+    // Add the headers required to serve with wasm.
+    server.defaultResponseHeaders
+      ..add('Cross-Origin-Embedder-Policy', 'credentialless')
+      ..add('Cross-Origin-Opener-Policy', 'same-origin');
+
     // Serve requests in an error zone to prevent failures
     // when running from another error zone.
     runZonedGuarded(