Remove the last external import in protocol.

pkg/analysis_server/lib/src/protocol.dart

Index: pkg/analysis_server/lib/src/protocol.dart
diff --git a/pkg/analysis_server/lib/src/protocol.dart b/pkg/analysis_server/lib/src/protocol.dart
index 05baa33b8a2cd1e3392f25e4faf630b44e1ee799..83a10557781675d2e3ff15ae7b53719dc75e67ee 100644
--- a/pkg/analysis_server/lib/src/protocol.dart
+++ b/pkg/analysis_server/lib/src/protocol.dart
@@ -7,8 +7,6 @@ library protocol;
 import 'dart:collection';
 import 'dart:convert';
 
-import 'package:analysis_server/src/services/json.dart';
-
 part 'generated_protocol.dart';
 
 
@@ -234,6 +232,19 @@ RefactoringOptions _refactoringOptionsFromJson(JsonDecoder jsonDecoder,
  */
 typedef Object JsonDecoderCallback(String jsonPath, Object value);
 
+
+/**
+ * Instances of the class [HasToJson] implement [toJson] method that returns
+ * a JSON presentation.
+ */
+abstract class HasToJson {
+  /**
+   * Returns a JSON presentation of the object.
+   */
+  Map<String, Object> toJson();
+}
+
+
 /**
  * Base class for decoding JSON objects.  The derived class must implement
  * error reporting logic.