moved minimum_gas_price from EthEngine to Engine and wired it in hbbf…

…t_engine.

crates/ethcore/src/engines/hbbft/hbbft_engine.rs

@@ -1286,6 +1286,10 @@ impl Engine<EthereumMachine> for HoneyBadgerBFT {
         &self.machine
     }
 
+    fn minimum_gas_price(&self) -> Option<U256> {
+        self.current_minimum_gas_price.lock().clone()
+    }
+
     fn fork_choice(&self, new: &ExtendedHeader, current: &ExtendedHeader) -> ForkChoice {
         crate::engines::total_difficulty_fork_choice(new, current)
     }

crates/ethcore/src/engines/mod.rs

@@ -492,6 +492,12 @@ pub trait Engine<M: Machine>: Sync + Send {
         true
     }
 
+    /// Some Engine might define the minimum gas price by themselve.
+    /// (for example: contract)
+    fn minimum_gas_price(&self) -> Option<U256> {
+        None
+    }
+
     /// Sign using the EngineSigner, to be used for consensus tx signing.
     fn sign(&self, _hash: H256) -> Result<Signature, M::Error> {
         unimplemented!()
@@ -709,12 +715,6 @@ pub trait EthEngine: Engine<::machine::EthereumMachine> {
     fn allow_non_eoa_sender(&self, best_block_number: BlockNumber) -> bool {
         self.params().eip3607_transition > best_block_number
     }
-
-    /// Some Engine might define the minimum gas price by themselve.
-    /// (for example: contract)
-    fn minimum_gas_price(&self) -> Option<U256> {
-        None
-    }
 }
 
 // convenience wrappers for existing functions.