Add flag to control CORS header ethereum#394

* Disabled on CLI
* http://localhost on Mist

cmd/geth/main.go

@@ -233,6 +233,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 		utils.VMDebugFlag,
 		utils.ProtocolVersionFlag,
 		utils.NetworkIdFlag,
+		utils.RPCCORSDomainFlag,
 	}
 
 	// missing:

cmd/mist/main.go

@@ -47,12 +47,19 @@ var (
 		Usage: "absolute path to GUI assets directory",
 		Value: common.DefaultAssetPath(),
 	}
+	rpcCorsFlag = utils.RPCCORSDomainFlag
 )
 
 func init() {
+	// Mist-specific default
+	if len(rpcCorsFlag.Value) == 0 {
+		rpcCorsFlag.Value = "http://localhost"
+	}
+
 	app.Action = run
 	app.Flags = []cli.Flag{
 		assetPathFlag,
+		rpcCorsFlag,
 
 		utils.BootnodesFlag,
 		utils.DataDirFlag,

cmd/utils/flags.go

@@ -148,7 +148,11 @@ var (
 		Usage: "Port on which the JSON-RPC server should listen",
 		Value: 8545,
 	}
-
+	RPCCORSDomainFlag = cli.StringFlag{
+		Name:  "rpccorsdomain",
+		Usage: "Domain on which to send Access-Control-Allow-Origin header",
+		Value: "",
+	}
 	// Network Settings
 	MaxPeersFlag = cli.IntFlag{
 		Name:  "maxpeers",