Improve the handling of the connection header

runtime/bin/http.dart

Index: runtime/bin/http.dart
diff --git a/runtime/bin/http.dart b/runtime/bin/http.dart
index b0ebda607ee356eec82d8935365890a4a9b7112f..b6b4f2ea173e43b96511298911f9805b98971d8c 100644
--- a/runtime/bin/http.dart
+++ b/runtime/bin/http.dart
@@ -306,6 +306,11 @@ interface HttpRequest default _HttpRequest {
   int get contentLength();
 
   /**
+   * Returns the persistent connection state signaled by the client.
+   */
+  bool get persistentConnection();
+
+  /**
    * Returns the method for the request.
    */
   String get method();
@@ -368,6 +373,13 @@ interface HttpResponse default _HttpResponse {
   String reasonPhrase;
 
   /**
+   * Gets and sets the persistent connection state. The initial value
+   * of this property is the persistent connection state from the
+   * request.
+   */
+  bool persistentConnection;
+
+  /**
    * Returns the response headers.
    */
   HttpHeaders get headers();