Make threadpool::Runtime methods take &self (#1140)

The runtime is inherently multi-threaded, so it's going to have to deal
with synchronization when submitting new tasks anyway. This allows a
runtime to be shared by multiple threads more easily when e.g. building
a blocking facade over a tokio-based API.

tokio-tls/tests/bad.rs

@@ -89,7 +89,7 @@ fn get_host(host: &'static str) -> Error {
     let addr = format!("{}:443", host);
     let addr = t!(addr.to_socket_addrs()).next().unwrap();
 
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
     let client = TcpStream::connect(&addr);
     let data = client.and_then(move |socket| {
         let builder = TlsConnector::builder();

tokio-tls/tests/google.rs

@@ -63,7 +63,7 @@ fn fetch_google() {
     let addr = t!("google.com:443".to_socket_addrs()).next().unwrap();
 
     // Create an event loop and connect a socket to our resolved address.c
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
     let client = TcpStream::connect(&addr);
 
     // Send off the request by first negotiating an SSL handshake, then writing
@@ -97,7 +97,7 @@ fn wrong_hostname_error() {
 
     let addr = t!("google.com:443".to_socket_addrs()).next().unwrap();
 
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
     let client = TcpStream::connect(&addr);
     let data = client.and_then(move |socket| {
         let builder = TlsConnector::builder();

tokio-tls/tests/smoke.rs

@@ -507,7 +507,7 @@ const AMT: u64 = 128 * 1024;
 #[test]
 fn client_to_server() {
     drop(env_logger::try_init());
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
 
     // Create a server listening on a port, then figure out what that port is
     let srv = t!(TcpListener::bind(&t!("127.0.0.1:0".parse())));
@@ -540,7 +540,7 @@ fn client_to_server() {
 #[test]
 fn server_to_client() {
     drop(env_logger::try_init());
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
 
     // Create a server listening on a port, then figure out what that port is
     let srv = t!(TcpListener::bind(&t!("127.0.0.1:0".parse())));
@@ -597,7 +597,7 @@ impl<S: AsyncWrite> AsyncWrite for OneByte<S> {
 fn one_byte_at_a_time() {
     const AMT: u64 = 1024;
     drop(env_logger::try_init());
-    let mut l = t!(Runtime::new());
+    let l = t!(Runtime::new());
 
     let srv = t!(TcpListener::bind(&t!("127.0.0.1:0".parse())));
     let addr = t!(srv.local_addr());