Mark the name in an extension as being in a declaration context
Mark the name in an extension as being in a declaration context

Change-Id: I3300b9042b62d47af3e23959875695741decc302
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108160
Commit-Queue: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Dan Rubel <5c5a7a1a3f9344592135bed55605519045cfa711@google.com>
Auto-Submit: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Reviewed-by: Dan Rubel <5c5a7a1a3f9344592135bed55605519045cfa711@google.com>

dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk