Add the --build-summary-exclude-informative flag.

pkg/analyzer/tool/summary/generate.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This file contains code to generate serialization/deserialization logic for
  * summaries based on an "IDL" description of the summary format (written in
  * stylized Dart).
  *
  * For each class in the "IDL" input, two corresponding classes are generated:
@@ skipping 265 matching lines @@
                 type.typeArguments != null &&
                 type.typeArguments.arguments.length == 1) {
               isList = true;
               type = type.typeArguments.arguments[0];
             }
             if (type.typeArguments != null) {
               throw new Exception('Cannot handle type arguments in `$type`');
             }
             int id;
             bool isDeprecated = false;
+            bool isInformative = false;
             for (Annotation annotation in classMember.metadata) {
               if (annotation.name.name == 'Id') {
                 if (id != null) {
                   throw new Exception(
                       'Duplicate @id annotation ($classMember)');
                 }
                 if (annotation.arguments.arguments.length != 1) {
                   throw new Exception(
                       '@Id must be passed exactly one argument ($desc)');
                 }
                 Expression expression = annotation.arguments.arguments[0];
                 if (expression is IntegerLiteral) {
                   id = expression.value;
                 } else {
                   throw new Exception(
                       '@Id parameter must be an integer literal ($desc)');
                 }
               } else if (annotation.name.name == 'deprecated') {
                 if (annotation.arguments != null) {
                   throw new Exception('@deprecated does not take args ($desc)');
                 }
                 isDeprecated = true;
+              } else if (annotation.name.name == 'informative') {
+                isInformative = true;
               }
             }
             if (id == null) {
               throw new Exception('Missing @id annotation ($desc)');
             }
             String doc = _getNodeDoc(lineInfo, classMember);
             idlModel.FieldType fieldType =
                 new idlModel.FieldType(type.name.name, isList);
             cls.allFields.add(new idlModel.FieldDeclaration(
-                doc, classMember.name.name, fieldType, id, isDeprecated));
+                doc,
+                classMember.name.name,
+                fieldType,
+                id,
+                isDeprecated,
+                isInformative));
           } else if (classMember is ConstructorDeclaration &&
               classMember.name.name == 'fromBuffer') {
             // Ignore `fromBuffer` declarations; they simply forward to the
             // read functions generated by [_generateReadFunction].
           } else {
             throw new Exception('Unexpected class member `$classMember`');
           }
         }
       } else if (decl is EnumDeclaration) {
         String doc = _getNodeDoc(lineInfo, decl);
@@ skipping 254 matching lines @@
       // Generate constructor.
       out();
       out('$builderName({${constructorParams.join(', ')}})');
       List<idlModel.FieldDeclaration> fields = cls.fields.toList();
       for (int i = 0; i < fields.length; i++) {
         idlModel.FieldDeclaration field = fields[i];
         String prefix = i == 0 ? '  : ' : '    ';
         String suffix = i == fields.length - 1 ? ';' : ',';
         out('${prefix}_${field.name} = ${field.name}$suffix');
       }
+      // Generate flushInformative().
+      {
+        out();
+        out('/**');
+        out(' * Flush [informative] data recursively.');
+        out(' */');
+        out('void flushInformative() {');
+        indent(() {
+          for (idlModel.FieldDeclaration field in cls.fields) {
+            idlModel.FieldType fieldType = field.type;
+            String valueName = '_' + field.name;
+            if (field.isInformative) {
+              out('$valueName = null;');
+            } else if (_idl.classes.containsKey(fieldType.typeName)) {
+              if (fieldType.isList) {
+                out('$valueName?.forEach((b) => b.flushInformative());');
+              } else {
+                out('$valueName?.flushInformative();');
+              }
+            }
+          }
+        });
+        out('}');
+      }
       // Generate finish.
       if (cls.isTopLevel) {
         out();
         out('List<int> toBuffer() {');
         indent(() {
           out('fb.Builder fbBuilder = new fb.Builder();');
           String fileId = cls.fileIdentifier == null
               ? ''
               : ', ${quoted(cls.fileIdentifier)}';
           out('return fbBuilder.finish(finish(fbBuilder)$fileId);');
@@ skipping 303 matching lines @@
       return token.lexeme.split('\n').map((String line) {
         if (line.startsWith(indent)) {
           line = line.substring(indent.length);
         }
         return line;
       }).join('\n');
     }
     return null;
   }
 }