Add quick-fix to convert child: to children:

pkg/analysis_server/test/services/correction/fix_test.dart

Index: pkg/analysis_server/test/services/correction/fix_test.dart
diff --git a/pkg/analysis_server/test/services/correction/fix_test.dart b/pkg/analysis_server/test/services/correction/fix_test.dart
index 6c414641ad23e70cca3c70d701048969199727ca..7ed9aea68bd005c64de354bad37c9a0ae5a0b7e3 100644
--- a/pkg/analysis_server/test/services/correction/fix_test.dart
+++ b/pkg/analysis_server/test/services/correction/fix_test.dart
@@ -27,6 +27,7 @@ import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../../abstract_single_unit.dart';
+import 'flutter_util.dart';
 
 main() {
   defineReflectiveSuite(() {
@@ -53,6 +54,8 @@ class BaseFixProcessorTest extends AbstractSingleUnitTest {
 
   String myPkgLibPath = '/packages/my_pkg/lib';
 
+  String flutterPkgLibPath = '/packages/flutter/lib';
+
   Fix fix;
   SourceChange change;
   String resultCode;
@@ -5387,6 +5390,135 @@ class A {
 ''');
   }
 
+  test_undefinedParameter_convertFlutterChild_invalidList() async {
+    _configureFlutterPkg({
+      'src/widgets/framework.dart': flutter_framework_code,
+    });
+    await resolveTestUnit('''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Container(
+    child: new Row(
+      child: <Widget>[
+        new Transform(),
+        null,
+        new AspectRatio(),
+      ],
+    ),
+  );
+}
+''');
+    await assertNoFix(DartFixKind.CONVERT_FLUTTER_CHILD);
+  }
+
+  test_undefinedParameter_convertFlutterChild_OK_hasList() async {
+    _configureFlutterPkg({
+      'src/widgets/framework.dart': flutter_framework_code,
+    });
+    await resolveTestUnit('''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Container(
+    child: new Row(
+      child: [
+        new Transform(),
+        new ClipRect.rect(),
+        new AspectRatio(),
+      ],
+    ),
+  );
+}
+''');
+    await assertHasFix(
+        DartFixKind.CONVERT_FLUTTER_CHILD,
+        '''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Container(
+    child: new Row(
+      children: <Widget>[
+        new Transform(),
+        new ClipRect.rect(),
+        new AspectRatio(),
+      ],
+    ),
+  );
+}
+''');
+  }
+
+  test_undefinedParameter_convertFlutterChild_OK_hasTypedList() async {
+    _configureFlutterPkg({
+      'src/widgets/framework.dart': flutter_framework_code,
+    });
+    await resolveTestUnit('''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Container(
+    child: new Row(
+      child: <Widget>[
+        new Transform(),
+        new ClipRect.rect(),
+        new AspectRatio(),
+      ],
+    ),
+  );
+}
+''');
+    await assertHasFix(
+        DartFixKind.CONVERT_FLUTTER_CHILD,
+        '''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Container(
+    child: new Row(
+      children: <Widget>[
+        new Transform(),
+        new ClipRect.rect(),
+        new AspectRatio(),
+      ],
+    ),
+  );
+}
+''');
+  }
+
+  test_undefinedParameter_convertFlutterChild_OK_multiLine() async {
+    _configureFlutterPkg({
+      'src/widgets/framework.dart': flutter_framework_code,
+    });
+    await resolveTestUnit('''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Scaffold(
+    body: new Row(
+      child: new Container(
+        width: 200.0,
+        height: 300.0,
+      ),
+    ),
+  );
+}
+''');
+    await assertHasFix(
+        DartFixKind.CONVERT_FLUTTER_CHILD,
+        '''
+import 'package:flutter/src/widgets/framework.dart';
+build() {
+  return new Scaffold(
+    body: new Row(
+      children: <Widget>[
+        new Container(
+          width: 200.0,
+          height: 300.0,
+        ),
+      ],
+    ),
+  );
+}
+''');
+  }
+
   test_undefinedSetter_useSimilar_hint() async {
     await resolveTestUnit('''
 class A {
@@ -5524,6 +5656,34 @@ class Required {
 }
 ''');
   }
+
+  /**
+   * Configures the [SourceFactory] to have the `flutter` package in
+   * `/packages/flutter/lib` folder.
+   */
+  void _configureFlutterPkg(Map<String, String> pathToCode) {
+    pathToCode.forEach((path, code) {
+      provider.newFile('$flutterPkgLibPath/$path', code);
+    });
+    // configure SourceFactory
+    Folder myPkgFolder = provider.getResource(flutterPkgLibPath);
+    UriResolver pkgResolver = new PackageMapUriResolver(provider, {
+      'flutter': [myPkgFolder]
+    });
+    SourceFactory sourceFactory = new SourceFactory(
+        [new DartUriResolver(sdk), pkgResolver, resourceResolver]);
+    if (enableNewAnalysisDriver) {
+      driver.configure(sourceFactory: sourceFactory);
+    } else {
+      context.sourceFactory = sourceFactory;
+    }
+    // force 'flutter' resolution
+    addSource(
+        '/tmp/other.dart',
+        pathToCode.keys
+            .map((path) => "import 'package:flutter/$path';")
+            .join('\n'));
+  }
 }
 
 @reflectiveTest