Make sure that a DropdownMenu doesn't crash in 0x0 environment (flutter#174809)

This is my attempt to handle
flutter#6537 for the DropdownMenu
widget.

Author: ahmedsameha1

packages/flutter/test/material/dropdown_menu_test.dart

@@ -4853,6 +4853,30 @@ void main() {
       expect(controller.text, TestMenu.mainMenu1.label);
     },
   );
+
+  testWidgets('DropdownMenu does not crash at zero area', (WidgetTester tester) async {
+    tester.view.physicalSize = Size.zero;
+    final TextEditingController controller = TextEditingController(text: 'I');
+    addTearDown(controller.dispose);
+    addTearDown(tester.view.reset);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: DropdownMenu<TestMenu>(
+              dropdownMenuEntries: menuChildren,
+              controller: controller,
+            ),
+          ),
+        ),
+      ),
+    );
+    expect(tester.getSize(find.byType(DropdownMenu<TestMenu>)), Size.zero);
+    controller.selection = const TextSelection.collapsed(offset: 0);
+    await tester.pump();
+    expect(find.byType(MenuItemButton), findsWidgets);
+  });
 }
 
 enum TestMenu {