Generate an error for active connections when the HTTP client is shutdown

tests/standalone/io/http_server_early_client_close_test.dart

Index: tests/standalone/io/http_server_early_client_close_test.dart
diff --git a/tests/standalone/io/http_server_early_client_close_test.dart b/tests/standalone/io/http_server_early_client_close_test.dart
index 66a2b06d28d87767bcf14c2d0811bc4551f7d2ce..5d23fc4be9f56f00dc760f3959f18974c657705c 100644
--- a/tests/standalone/io/http_server_early_client_close_test.dart
+++ b/tests/standalone/io/http_server_early_client_close_test.dart
@@ -63,17 +63,18 @@ void testEarlyClose() {
   // The empty packet is valid.
 
   // Close while sending header
-  add("G", "Connection closed before full header was received");
-  add("GET /", "Connection closed before full header was received");
-  add("GET / HTTP/1.1", "Connection closed before full header was received");
-  add("GET / HTTP/1.1\r\n", "Connection closed before full header was received");
+  String message = "Connection closed before full request header was received";
+  add("G", message);
+  add("GET /", message);
+  add("GET / HTTP/1.1", message);
+  add("GET / HTTP/1.1\r\n", message);
 
   // Close while sending content
   add("GET / HTTP/1.1\r\nContent-Length: 100\r\n\r\n",
-      "Connection closed before full body was received",
+      "Connection closed before full request body was received",
       expectRequest: true);
   add("GET / HTTP/1.1\r\nContent-Length: 100\r\n\r\n1",
-      "Connection closed before full body was received",
+      "Connection closed before full request body was received",
       expectRequest: true);