Revert "Add a way to get the furthest Navigator" (#12608)

* Revert "BoxDecoration.borderRadius and RoundedRectangleBorder.borderRadius RTL (#12603)"

This reverts commit 07908916.

* Revert "Copy snapshot file into assets (#12523)"

This reverts commit f6135107.

* Revert "Add a rootNavigator option to Navigator.of (#12580)"

This reverts commit 822084b2.

packages/flutter/lib/src/cupertino/dialog.dart

@@ -53,9 +53,6 @@ const BoxDecoration _kCupertinoDialogBackFill = const BoxDecoration(
 /// dialog. Rather than using this widget directly, consider using
 /// [CupertinoAlertDialog], which implement a specific kind of dialog.
 ///
-/// Push with `Navigator.of(..., rootNavigator: true)` when using with
-/// [CupertinoTabScaffold] to ensure that the dialog appears above the tabs.
-///
 /// See also:
 ///
 ///  * [CupertinoAlertDialog], which is a dialog with title, contents, and

packages/flutter/lib/src/material/dialog.dart

@@ -461,7 +461,7 @@ Future<T> showDialog<T>({
   bool barrierDismissible: true,
   @required Widget child,
 }) {
-  return Navigator.of(context, rootNavigator: true).push(new _DialogRoute<T>(
+  return Navigator.push(context, new _DialogRoute<T>(
     child: child,
     theme: Theme.of(context, shadowThemeOnly: true),
     barrierDismissible: barrierDismissible,

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

@@ -2003,17 +2003,6 @@ abstract class BuildContext {
   /// ```
   State ancestorStateOfType(TypeMatcher matcher);
 
-  /// Returns the [State] object of the furthest ancestor [StatefulWidget] widget
-  /// that matches the given [TypeMatcher].
-  ///
-  /// Functions the same way as [ancestorStateOfType] but keeps visiting subsequent
-  /// ancestors until there are none of the type matching [TypeMatcher] remaining.
-  /// Then returns the last one found.
-  ///
-  /// This operation is O(N) as well though N is the entire widget tree rather than
-  /// a subtree.
-  State rootAncestorStateOfType(TypeMatcher matcher);
-
   /// Returns the [RenderObject] object of the nearest ancestor [RenderObjectWidget] widget
   /// that matches the given [TypeMatcher].
   ///
@@ -3256,19 +3245,6 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
     return statefulAncestor?.state;
   }
 
-  @override
-  State rootAncestorStateOfType(TypeMatcher matcher) {
-    assert(_debugCheckStateIsActiveForAncestorLoopkup());
-    Element ancestor = _parent;
-    StatefulElement statefulAncestor;
-    while (ancestor != null) {
-      if (ancestor is StatefulElement && matcher.check(ancestor.state))
-        statefulAncestor = ancestor;
-      ancestor = ancestor._parent;
-    }
-    return statefulAncestor?.state;
-  }
-
   @override
   RenderObject ancestorRenderObjectOfType(TypeMatcher matcher) {
     assert(_debugCheckStateIsActiveForAncestorLoopkup());

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

@@ -708,17 +708,8 @@ class Navigator extends StatefulWidget {
   ///   ..pop()
   ///   ..pushNamed('/settings');
   /// ```
-  ///
-  /// If `rootNavigator` is set to true, the state from the furthest instance of
-  /// this class is given instead. Useful for pushing contents above all subsequent
-  /// instances of [Navigator].
-  static NavigatorState of(
-    BuildContext context, {
-      bool rootNavigator: false
-    }) {
-    final NavigatorState navigator = rootNavigator
-        ? context.rootAncestorStateOfType(const TypeMatcher<NavigatorState>())
-        : context.ancestorStateOfType(const TypeMatcher<NavigatorState>());
+  static NavigatorState of(BuildContext context) {
+    final NavigatorState navigator = context.ancestorStateOfType(const TypeMatcher<NavigatorState>());
     assert(() {
       if (navigator == null) {
         throw new FlutterError(

packages/flutter/test/widgets/navigator_test.dart

@@ -179,73 +179,6 @@ void main() {
     expect('$exception', startsWith('Navigator operation requested with a context'));
   });
 
-  testWidgets('Navigator.of rootNavigator finds root Navigator', (WidgetTester tester) async {
-    await tester.pumpWidget(new MaterialApp(
-      home: new Material(
-        child: new Column(
-          children: <Widget>[
-            const SizedBox(
-              height: 300.0,
-              child: const Text('Root page'),
-            ),
-            new SizedBox(
-              height: 300.0,
-              child: new Navigator(
-                onGenerateRoute: (RouteSettings settings) {
-                  if (settings.isInitialRoute) {
-                    return new MaterialPageRoute<Null>(
-                      builder: (BuildContext context) {
-                        return new RaisedButton(
-                          child: const Text('Next'),
-                          onPressed: () {
-                            Navigator.of(context).push(
-                              new MaterialPageRoute<Null>(
-                                builder: (BuildContext context) {
-                                  return new RaisedButton(
-                                    child: const Text('Inner page'),
-                                    onPressed: () {
-                                      Navigator.of(context, rootNavigator: true).push(
-                                        new MaterialPageRoute<Null>(
-                                          builder: (BuildContext context) {
-                                            return const Text('Dialog');
-                                          }
-                                        ),
-                                      );
-                                    },
-                                  );
-                                }
-                              ),
-                            );
-                          },
-                        );
-                      },
-                    );
-                  }
-                },
-              ),
-            ),
-          ],
-        ),
-      ),
-    ));
-
-    await tester.tap(find.text('Next'));
-    await tester.pump();
-    await tester.pump(const Duration(milliseconds: 300));
-
-    // Both elements are on screen.
-    expect(tester.getTopLeft(find.text('Root page')).dy, 0.0);
-    expect(tester.getTopLeft(find.text('Inner page')).dy, greaterThan(300.0));
-
-    await tester.tap(find.text('Inner page'));
-    await tester.pump();
-    await tester.pump(const Duration(milliseconds: 300));
-
-    // Dialog is pushed to the whole page and is at the top of the screen, not
-    // inside the inner page.
-    expect(tester.getTopLeft(find.text('Dialog')).dy, 0.0);
-  });
-
   testWidgets('Gestures between push and build are ignored', (WidgetTester tester) async {
     final List<String> log = <String>[];
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{