Update beacon_chain as per test bugs

beacon_node/beacon_chain/src/finalized_head.rs

@@ -0,0 +1,34 @@
+use crate::{BeaconChain, CheckPoint, ClientDB, SlotClock};
+use std::sync::RwLockReadGuard;
+use types::{BeaconBlock, BeaconState, Hash256};
+
+impl<T, U> BeaconChain<T, U>
+where
+    T: ClientDB,
+    U: SlotClock,
+{
+    pub fn update_finalized_head(
+        &self,
+        new_beacon_block: BeaconBlock,
+        new_beacon_block_root: Hash256,
+        new_beacon_state: BeaconState,
+        new_beacon_state_root: Hash256,
+    ) {
+        let mut finalized_head = self
+            .finalized_head
+            .write()
+            .expect("CRITICAL: finalized_head poisioned.");
+        finalized_head.update(
+            new_beacon_block,
+            new_beacon_block_root,
+            new_beacon_state,
+            new_beacon_state_root,
+        );
+    }
+
+    pub fn finalized_head(&self) -> RwLockReadGuard<CheckPoint> {
+        self.finalized_head
+            .read()
+            .expect("CRITICAL: finalized_head poisioned.")
+    }
+}