Add the ability to get info of a Http connection, e.g. host and port.

runtime/bin/http_impl.dart

Index: runtime/bin/http_impl.dart
diff --git a/runtime/bin/http_impl.dart b/runtime/bin/http_impl.dart
index ef590d78287710c3954d4b63c05ce7799676cc8f..c664c512ca6bce3de537be4395153ad939e7dd1a 100644
--- a/runtime/bin/http_impl.dart
+++ b/runtime/bin/http_impl.dart
@@ -707,6 +707,8 @@ class _HttpRequestResponseBase {
     _bodyBytesWritten += bytes;
   }
 
+  HttpConnectionInfo get connectionInfo() => _httpConnection.connectionInfo;
+
   int _state;
   bool _headResponse;
 
@@ -1241,6 +1243,18 @@ class _HttpConnectionBase implements Hashable {
     return new _DetachedSocket(socket, _httpParser.unparsedData);
   }
 
+  HttpConnectionInfo get connectionInfo() {
+    if (_socket == null || _closing || _error) return null;
+    try {
+      _HttpConnectionInfo info = new _HttpConnectionInfo();
+      info.remoteHost = _socket.remoteHost;
+      info.remotePort = _socket.remotePort;
+      info.localPort = _socket.port;
+      return info;
+    } catch (var e) { }
+    return null;
+  }
+
   abstract void _onConnectionClosed(e);
   abstract void _responseDone();
 
@@ -2100,6 +2114,13 @@ class _HttpClient implements HttpClient {
 }
 
 
+class _HttpConnectionInfo implements HttpConnectionInfo {
+  String remoteHost;
+  int remotePort;
+  int localPort;
+}
+
+
 class _DetachedSocket implements DetachedSocket {
   _DetachedSocket(this._socket, this._unparsedData);
   Socket get socket() => _socket;