message: Blob asserts
  Server will dedup same content and return same ID.
  This was not accounted in asserts I've added, so changing them to make less strict.
diff: @@ -80,15 +80,15 @@ export class BlobManager {
  () => this.attachBlobCallback(response.id),
  );
  - assert(!this.pendingBlobIds.has(response.id));
  - assert(!this.blobIds.has(response.id));
  + // Note - server will de-dup blobs, so we might get existing blobId!
  + if (!this.blobIds.has(response.id)) {
  this.pendingBlobIds.add(response.id);
  + }
  return handle;
  }
  public addBlobId(blobId: string) {
  - assert(!this.blobIds.has(blobId));
  this.blobIds.add(blobId);
  this.pendingBlobIds.delete(blobId);
  }
  