add analysis server --flutter-repo startup flag

pkg/analyzer/lib/src/context/builder.dart

Index: pkg/analyzer/lib/src/context/builder.dart
diff --git a/pkg/analyzer/lib/src/context/builder.dart b/pkg/analyzer/lib/src/context/builder.dart
index fe138d372793a38b5c84634dafa952963f09d98b..4f79e23469777065983169b906c3c1927072b285 100644
--- a/pkg/analyzer/lib/src/context/builder.dart
+++ b/pkg/analyzer/lib/src/context/builder.dart
@@ -29,6 +29,7 @@ import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/workspace.dart';
 import 'package:analyzer/src/lint/registry.dart';
+import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/summary/summary_sdk.dart';
 import 'package:analyzer/src/task/options.dart';
 import 'package:args/args.dart';
@@ -458,6 +459,17 @@ class ContextBuilder {
           verbose('Using default lint rules');
         }
       }
+      if (ContextBuilderOptions.flutterRepo) {
+        const lintName = 'public_member_api_docs';
+        Linter rule = options.lintRules.firstWhere(
+            (Linter lint) => lint.name == lintName,
+            orElse: () => null);
+        if (rule == null) {
+          rule = Registry.ruleRegistry
+              .firstWhere((Linter lint) => lint.name == lintName);
+          options.lintRules = new List.from(options.lintRules)..add(rule);
+        }
+      }
     } else {
       verbose('Using default analysis options');
     }
@@ -609,6 +621,12 @@ class ContextBuilder {
  */
 class ContextBuilderOptions {
   /**
+   * A flag indicating that the flutter repository is being analyzed.
+   * See comments in source for `flutter analyze --watch`.
+   */
+  static bool flutterRepo = false;
+
+  /**
    * The results of parsing the command line arguments as defined by
    * [defineAnalysisArguments] or `null` if none.
    */