Enable standalone/io/http_test, splitting it into three separate tests.

runtime/bin/http.dart

Index: runtime/bin/http.dart
diff --git a/runtime/bin/http.dart b/runtime/bin/http.dart
index 5e2f45e16b6e2e0fb963c3a9d111649efaf334c6..d18ed339d2eb0ded2678f0d3d9e56cd026d5922a 100644
--- a/runtime/bin/http.dart
+++ b/runtime/bin/http.dart
@@ -717,11 +717,11 @@ interface HttpClientConnection {
    * Set this property to [:true:] if this connection should
    * automatically follow redirects. The default is [:true:].
    */
-  bool followRedirect;
+  bool followRedirects;
 
   /**
    * Set this property to the maximum number of redirects to follow
-   * when [followRedirect] is [:true:]. If this number is exceeded the
+   * when [followRedirects] is [:true:]. If this number is exceeded the
    * [onError] callback will be called with a [RedirectLimitExceeded]
    * exception. The default value is 5.
    */
@@ -775,6 +775,12 @@ interface HttpClientRequest default _HttpClientRequest {
   List<Cookie> get cookies();
 
   /**
+   * Gets and sets the requested persistent connection state.
+   * The default value is [:true:].
+   */
+  bool persistentConnection;
+
+  /**
    * Returns the output stream for the request. This is used to write
    * the request data. When all request data has been written close
    * the stream to indicate the end of the request.
@@ -808,6 +814,11 @@ interface HttpClientResponse default _HttpClientResponse {
   int get contentLength();
 
   /**
+   * Gets the persistent connection state returned by the server.
+   */
+  bool get persistentConnection();
+
+  /**
    * Returns whether the status code is one of the normal redirect
    * codes [:HttpStatus.MOVED_PERMANENTLY:], [:HttpStatus.FOUND:],
    * [:HttpStatus.MOVED_TEMPORARILY:], [:HttpStatus.SEE_OTHER:] and