[ Observatory ] Disable 'getWebSocketTarget' connection flow while DDS is disabled
[ Observatory ] Disable 'getWebSocketTarget' connection flow while DDS
is disabled

Invoking 'getWebSocketTarget' as an HTTP request seems to cause failures
with Flutter, resulting in a 403 response. Disabling this flow while DDS
is turned off in both the standalone VM and flutter_tools to resolve https://github.com/flutter/flutter/issues/64333

Change-Id: I862e616e622efd3701f10ed0616562cbd2663109
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/159643
Reviewed-by: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>
Commit-Queue: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk