Use a more precise type for "object" in analysis server API.

pkg/analysis_server/tool/spec/codegen_dart_protocol.dart

Index: pkg/analysis_server/tool/spec/codegen_dart_protocol.dart
diff --git a/pkg/analysis_server/tool/spec/codegen_dart_protocol.dart b/pkg/analysis_server/tool/spec/codegen_dart_protocol.dart
index 2136f0df63de0c2a88ff3c9d9fa08c577e710e7e..6eb74ed17b54937896d809c42dcb8b67c4a79bed 100644
--- a/pkg/analysis_server/tool/spec/codegen_dart_protocol.dart
+++ b/pkg/analysis_server/tool/spec/codegen_dart_protocol.dart
@@ -190,7 +190,7 @@ class CodegenProtocolVisitor extends HierarchicalApiVisitor with CodeGenerator {
    * Type references in the spec that are named something else in Dart.
    */
   static const Map<String, String> _typeRenames = const {
-    'object': 'Object',
+    'object': 'Map',
   };
 
   /**
@@ -291,7 +291,7 @@ class CodegenProtocolVisitor extends HierarchicalApiVisitor with CodeGenerator {
         toHtmlVisitor.showType(null, impliedType.type);
       }
     }));
-    writeln('class $className {');
+    writeln('class $className implements HasToJson {');
     indent(() {
       if (emitSpecialStaticMembers(className)) {
         writeln();