Handle closing of HTTP client and server

runtime/bin/socket.dart

Index: runtime/bin/socket.dart
diff --git a/runtime/bin/socket.dart b/runtime/bin/socket.dart
index 532b1e28bcb41e869508da71e44a8e38d292717f..ad48172bf596e8a03ec49c1e9a1a77480b198405 100644
--- a/runtime/bin/socket.dart
+++ b/runtime/bin/socket.dart
@@ -32,7 +32,7 @@ interface ServerSocket default _ServerSocket {
 }
 
 
-interface Socket default _Socket {
+interface Socket extends Hashable default _Socket {
   /**
    * Constructs a new socket and connects it to the given host on the given
    * port.
@@ -113,6 +113,11 @@ interface Socket default _Socket {
    * [onClosed].
    */
   void close([bool halfClose]);
+
+  /**
+   * Socket is hashable.
+   */
+  int hashCode();
 }