Move Commit from including the round to including the round's end_time

The round was usable to build the current clock in an accumulated 
fashion, relative to the previous round. The end time is the absolute 
metric of it, which can be used to calculate the round number (with all 
previous end times).

Substrate now builds off the best block, not genesis, using the end time 
included in the justification to start its machine in a synchronized 
state.

Knowing the end time of a round, or the round in which block was 
committed to, is necessary for nodes to sync up with Tendermint. 
Encoding it in the commit ensures it's long lasting and makes it readily 
available, without the load of an entire transaction.

substrate/consensus/src/import_queue.rs

@@ -3,9 +3,9 @@ use std::{
   sync::{Arc, RwLock},
   task::{Poll, Context},
   future::Future,
-  time::SystemTime,
 };
 
+use sp_core::Decode;
 use sp_inherents::CreateInherentDataProviders;
 use sp_runtime::traits::{Header, Block};
 use sp_api::{BlockId, TransactionFor};
@@ -18,9 +18,14 @@ use sc_client_api::Backend;
 
 use substrate_prometheus_endpoint::Registry;
 
-use tendermint_machine::{ext::BlockNumber, TendermintMachine};
+use tendermint_machine::{
+  ext::{BlockNumber, Commit},
+  TendermintMachine,
+};
 
 use crate::{
+  CONSENSUS_ID,
+  signature_scheme::TendermintSigner,
   tendermint::{TendermintClient, TendermintImport},
   Announce,
 };
@@ -98,12 +103,31 @@ where
   let authority = {
     let machine_clone = import.machine.clone();
     let mut import_clone = import.clone();
+    let best = import.client.info().best_number;
     async move {
       *machine_clone.write().unwrap() = Some(TendermintMachine::new(
         import_clone.clone(),
         // TODO
         0,
-        (BlockNumber(1), SystemTime::now()),
+        (
+          // Header::Number: TryInto<u64> doesn't implement Debug and can't be unwrapped
+          match best.try_into() {
+            Ok(best) => BlockNumber(best),
+            Err(_) => panic!("BlockNumber exceeded u64"),
+          },
+          Commit::<TendermintSigner>::decode(
+            &mut import_clone
+              .client
+              .justifications(&BlockId::Number(best))
+              .unwrap()
+              .unwrap()
+              .get(CONSENSUS_ID)
+              .unwrap()
+              .as_ref(),
+          )
+          .unwrap()
+          .end_time,
+        ),
         import_clone
           .get_proposal(&import_clone.client.header(BlockId::Number(0u8.into())).unwrap().unwrap())
           .await,

substrate/consensus/src/tendermint.rs

@@ -24,7 +24,7 @@ use sp_consensus::{Error, BlockOrigin, Proposer, Environment};
 use sc_consensus::{ForkChoiceStrategy, BlockImportParams, BlockImport, import_queue::IncomingBlock};
 
 use sc_service::ImportQueue;
-use sc_client_api::{Backend, Finalizer};
+use sc_client_api::{BlockBackend, Backend, Finalizer};
 
 use tendermint_machine::{
   ext::{BlockError, Commit, Network},
@@ -43,6 +43,7 @@ pub trait TendermintClient<B: Block, Be: Backend<B> + 'static>:
   Send
   + Sync
   + HeaderBackend<B>
+  + BlockBackend<B>
   + BlockImport<B, Transaction = TransactionFor<Self, B>>
   + Finalizer<B, Be>
   + ProvideRuntimeApi<B>
@@ -55,6 +56,7 @@ impl<
     C: Send
       + Sync
       + HeaderBackend<B>
+      + BlockBackend<B>
       + BlockImport<B, Transaction = TransactionFor<C, B>>
       + Finalizer<B, Be>
       + ProvideRuntimeApi<B>
@@ -379,8 +381,8 @@ where
       let info = self.client.info();
       assert_eq!(info.best_hash, parent);
       assert_eq!(info.finalized_hash, parent);
-      assert_eq!(info.best_number, number - 1);
-      assert_eq!(info.finalized_number, number - 1);
+      assert_eq!(info.best_number, number - 1u8.into());
+      assert_eq!(info.finalized_number, number - 1u8.into());
     }
 
     Ok(())