fix: SearchAnchor View not resizing when in nested navigator (#128357)

Similar to what was done on flutter/flutter#127198, look for the closest navigator instead of screen size.

Fixes: flutter/flutter#128344

Author: VictorOhashi

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

@@ -489,7 +489,8 @@ class _SearchViewRoute extends PopupRoute<_SearchViewRoute> {
   }
 
   void updateTweens(BuildContext context) {
-    final Size screenSize = MediaQuery.of(context).size;
+    final RenderBox navigator = Navigator.of(context).context.findRenderObject()! as RenderBox;
+    final Size screenSize = navigator.size;
     final Rect anchorRect = getRect() ?? Rect.zero;
 
     final BoxConstraints effectiveConstraints = viewConstraints ?? viewTheme.constraints ?? viewDefaults.constraints!;

packages/flutter/test/material/search_anchor_test.dart

@@ -1789,6 +1789,50 @@ void main() {
     expect(searchViewRect.topLeft, equals(const Offset(rootSpacing, rootSpacing)));
   });
 
+  testWidgets('Docked search view with nested navigator does not go off the screen', (WidgetTester tester) async {
+    addTearDown(tester.view.reset);
+    tester.view.physicalSize = const Size(400.0, 400.0);
+    tester.view.devicePixelRatio = 1.0;
+
+    const double rootSpacing = 100.0;
+
+    await tester.pumpWidget(MaterialApp(
+      builder: (BuildContext context, Widget? child) {
+        return Scaffold(
+          body: Padding(
+            padding: const EdgeInsets.all(rootSpacing),
+            child: child,
+          ),
+        );
+      },
+      home: Material(
+        child: Align(
+          alignment: Alignment.bottomRight,
+          child: SearchAnchor(
+            isFullScreen: false,
+            builder: (BuildContext context, SearchController controller) {
+              return IconButton(
+                icon: const Icon(Icons.search),
+                onPressed: () {
+                  controller.openView();
+                },
+              );
+            },
+            suggestionsBuilder: (BuildContext context, SearchController controller) {
+              return <Widget>[];
+            },
+          ),
+        ),
+      ),
+    ));
+
+    await tester.tap(find.byIcon(Icons.search));
+    await tester.pumpAndSettle();
+
+    final Rect searchViewRect = tester.getRect(find.descendant(of: findViewContent(), matching: find.byType(SizedBox)).first);
+    expect(searchViewRect.bottomRight, equals(const Offset(300.0, 300.0)));
+  });
+
 
   // Regression tests for https://github.com/flutter/flutter/issues/126623
   group('Overall InputDecorationTheme does not impact SearchBar and SearchView', () {