Eth JSON-RPC API: make EthLog#Data a string.

api/eth_types.go

@@ -545,8 +545,8 @@ type EthLog struct {
 	// Address is the address of the actor that produced the event log.
 	Address EthAddress `json:"address"`
 
-	// Data is the values of the event log, excluding topics
-	Data []EthHash `json:"data"`
+	// Data is the value of the event log, excluding topics
+	Data EthHash `json:"data"`
 
 	// List of topics associated with the event log.
 	Topics []EthHash `json:"topics"`

api/eth_types_test.go

@@ -176,7 +176,7 @@ func TestEthFilterResultMarshalJSON(t *testing.T) {
 		BlockHash:        hash2,
 		BlockNumber:      53,
 		Topics:           []EthHash{hash1},
-		Data:             []EthHash{hash1},
+		Data:             hash1,
 		Address:          addr,
 	}
 	logjson, err := json.Marshal(log)