Add fullscreenDialog argument in PageRouteBuilder (#40161)

packages/flutter/lib/src/widgets/pages.dart

@@ -56,7 +56,7 @@ class PageRouteBuilder<T> extends PageRoute<T> {
   /// Creates a route that delegates to builder callbacks.
   ///
   /// The [pageBuilder], [transitionsBuilder], [opaque], [barrierDismissible],
-  /// and [maintainState] arguments must not be null.
+  /// [maintainState], and [fullscreenDialog] arguments must not be null.
   PageRouteBuilder({
     RouteSettings settings,
     @required this.pageBuilder,
@@ -67,12 +67,14 @@ class PageRouteBuilder<T> extends PageRoute<T> {
     this.barrierColor,
     this.barrierLabel,
     this.maintainState = true,
+    bool fullscreenDialog = false,
   }) : assert(pageBuilder != null),
        assert(transitionsBuilder != null),
+       assert(opaque != null),
        assert(barrierDismissible != null),
        assert(maintainState != null),
-       assert(opaque != null),
-       super(settings: settings);
+       assert(fullscreenDialog != null),
+       super(settings: settings, fullscreenDialog: fullscreenDialog);
 
   /// Used build the route's primary contents.
   ///

packages/flutter/test/material/scaffold_test.dart

@@ -568,6 +568,15 @@ void main() {
       );
     }
 
+    PageRoute<void> pageRouteBuilder() {
+      return PageRouteBuilder<void>(
+        pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
+          return Scaffold(appBar: AppBar(), body: const Text('Page 2'));
+        },
+        fullscreenDialog: true,
+      );
+    }
+
     PageRoute<void> customPageRouteBuilder() {
       return _CustomPageRoute<void>(
         builder: (BuildContext context) {
@@ -589,6 +598,18 @@ void main() {
       await expectCloseIcon(tester, TargetPlatform.iOS, Icons.close, materialRouteBuilder);
     });
 
+    testWidgets('Close button shows correctly with PageRouteBuilder on Android', (WidgetTester tester) async {
+      await expectCloseIcon(tester, TargetPlatform.android, Icons.close, pageRouteBuilder);
+    });
+
+    testWidgets('Close button shows correctly with PageRouteBuilder on Fuchsia', (WidgetTester tester) async {
+      await expectCloseIcon(tester, TargetPlatform.fuchsia, Icons.close, pageRouteBuilder);
+    });
+
+    testWidgets('Close button shows correctly with PageRouteBuilder on iOS', (WidgetTester tester) async {
+      await expectCloseIcon(tester, TargetPlatform.iOS, Icons.close, pageRouteBuilder);
+    });
+
     testWidgets('Close button shows correctly with custom page route on Android', (WidgetTester tester) async {
       await expectCloseIcon(tester, TargetPlatform.android, Icons.close, customPageRouteBuilder);
     });