Ensure relay chain parent is the relay chain head (#103)

collator/src/lib.rs

@@ -25,6 +25,7 @@ use cumulus_primitives::{
 };
 use cumulus_runtime::ParachainBlockData;
 
+use sp_blockchain::HeaderBackend;
 use sp_consensus::{
 	BlockImport, BlockImportParams, BlockOrigin, Environment, Error as ConsensusError,
 	ForkChoiceStrategy, Proposal, Proposer, RecordProof,
@@ -350,14 +351,15 @@ where
 		polkadot_network: impl CollatorNetwork + Clone + 'static,
 	) -> Result<Self::ParachainContext, ()>
 	where
-		PClient: ProvideRuntimeApi<PBlock> + Send + Sync + BlockchainEvents<PBlock> + 'static,
+		PClient: ProvideRuntimeApi<PBlock> + BlockchainEvents<PBlock> + HeaderBackend<PBlock>
+			+ Send + Sync + 'static,
 		PClient::Api: RuntimeApiCollection<Extrinsic>,
 		<PClient::Api as ApiExt<PBlock>>::StateBackend: StateBackend<HashFor<PBlock>>,
 		Spawner: Spawn + Clone + Send + Sync + 'static,
 		Extrinsic: codec::Codec + Send + Sync + 'static,
 	{
 		self.delayed_block_announce_validator.set(
-			Box::new(JustifiedBlockAnnounceValidator::new(Vec::new(), polkadot_client.clone())),
+			Box::new(JustifiedBlockAnnounceValidator::new(polkadot_client.clone())),
 		);
 
 		let follow =