Revert r34269, as it broke the editor build

sdk/lib/_internal/pub/test/serve/web_socket/serve_directory_arg_errors_test.dart

Index: sdk/lib/_internal/pub/test/serve/web_socket/serve_directory_arg_errors_test.dart
===================================================================
--- sdk/lib/_internal/pub/test/serve/web_socket/serve_directory_arg_errors_test.dart	(revision 34273)
+++ sdk/lib/_internal/pub/test/serve/web_socket/serve_directory_arg_errors_test.dart	(working copy)
@@ -4,7 +4,6 @@
 
 library pub_tests;
 
-import 'package:json_rpc_2/error_code.dart' as rpc_error_code;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
@@ -23,29 +22,52 @@
     ]).create();
   });
 
+  integration("responds with an error if 'path' is missing", () {
+    pubServe();
+    expectWebSocketCall({
+      "command": "serveDirectory"
+    }, replyEquals: {
+      "code": "BAD_ARGUMENT",
+      "error": 'Missing "path" argument.'
+    });
+    endPubServe();
+  });
+
   integration("responds with an error if 'path' is not a string", () {
     pubServe();
-    expectWebSocketError("serveDirectory", {"path": 123},
-        rpc_error_code.INVALID_PARAMS,
-        'Parameter "path" for method "serveDirectory" must be a string, but '
-            'was 123.');
+    expectWebSocketCall({
+      "command": "serveDirectory",
+      "path": 123
+    }, replyEquals: {
+      "code": "BAD_ARGUMENT",
+      "error": '"path" must be a string. Got 123.'
+    });
     endPubServe();
   });
 
   integration("responds with an error if 'path' is absolute", () {
     pubServe();
-    expectWebSocketError("serveDirectory", {"path": "/absolute.txt"},
-        rpc_error_code.INVALID_PARAMS,
-        '"path" must be a relative path. Got "/absolute.txt".');
+    expectWebSocketCall({
+      "command": "serveDirectory",
+      "path": "/absolute.txt"
+    }, replyEquals: {
+      "code": "BAD_ARGUMENT",
+      "error": '"path" must be a relative path. Got "/absolute.txt".'
+    });
     endPubServe();
   });
 
   integration("responds with an error if 'path' reaches out", () {
     pubServe();
-    expectWebSocketError("serveDirectory", {"path": "a/../../bad.txt"},
-        rpc_error_code.INVALID_PARAMS,
-        '"path" cannot reach out of its containing directory. Got '
-            '"a/../../bad.txt".');
+    expectWebSocketCall({
+      "command": "serveDirectory",
+      "path": "a/../../bad.txt"
+    }, replyEquals: {
+      "code": "BAD_ARGUMENT",
+      "error":
+          '"path" cannot reach out of its containing directory. '
+          'Got "a/../../bad.txt".'
+    });
     endPubServe();
   });
 }