Accessibility fixes for new gallery (#16973)

examples/flutter_gallery/lib/gallery/backdrop.dart

@@ -46,7 +46,7 @@ class _IgnorePointerWhileStatusIsNotState extends State<_IgnorePointerWhileStatu
   void initState() {
     super.initState();
     widget.controller.addStatusListener(_handleStatusChange);
-    _ignoring = widget.controller.status != AnimationStatus.completed;
+    _ignoring = widget.controller.status != widget.status;
   }
 
   @override
@@ -283,7 +283,7 @@ class _BackdropState extends State<Backdrop> with SingleTickerProviderStateMixin
               ),
               trailing: new IconButton(
                 onPressed: _toggleFrontLayer,
-                tooltip: 'Show options page',
+                tooltip: 'Toggle options page',
                 icon: new AnimatedIcon(
                   icon: AnimatedIcons.close_menu,
                   progress: _controller,
@@ -328,6 +328,7 @@ class _BackdropState extends State<Backdrop> with SingleTickerProviderStateMixin
         ),
         new PositionedTransition(
           rect: frontRelativeRect,
+          child: new ExcludeSemantics(
             child: new Container(
               alignment: Alignment.topLeft,
               child: new GestureDetector(
@@ -339,6 +340,7 @@ class _BackdropState extends State<Backdrop> with SingleTickerProviderStateMixin
               ),
             ),
           ),
+        ),
       ],
     );
   }

examples/flutter_gallery/lib/gallery/options.dart

@@ -96,7 +96,8 @@ class _OptionsItem extends StatelessWidget {
   Widget build(BuildContext context) {
     final double textScaleFactor = MediaQuery.of(context)?.textScaleFactor ?? 1.0;
 
-    return new Container(
+    return new MergeSemantics(
+      child: new Container(
         constraints: new BoxConstraints(minHeight: _kItemHeight * textScaleFactor),
         padding: _kItemPadding,
         alignment: AlignmentDirectional.centerStart,
@@ -109,6 +110,7 @@ class _OptionsItem extends StatelessWidget {
             child: child,
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/test/drawer_test.dart

@@ -26,7 +26,7 @@ void main() {
     await tester.pump(); // triggers a frame
 
     // Show the options page
-    await tester.tap(find.byTooltip('Show options page'));
+    await tester.tap(find.byTooltip('Toggle options page'));
     await tester.pumpAndSettle();
 
     MaterialApp app = find.byType(MaterialApp).evaluate().first.widget;
@@ -89,7 +89,7 @@ void main() {
     expect(hasFeedback, true);
 
     // Hide the options page
-    await tester.tap(find.byTooltip('Show options page'));
+    await tester.tap(find.byTooltip('Toggle options page'));
     await tester.pumpAndSettle();
   });
 }

examples/flutter_gallery/test/simple_smoke_test.dart

@@ -16,7 +16,7 @@ void main() {
     await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
     await tester.pump(); // triggers a frame
 
-    final Finder showOptionsPageButton = find.byTooltip('Show options page');
+    final Finder showOptionsPageButton = find.byTooltip('Toggle options page');
 
     // Show the options page
     await tester.tap(showOptionsPageButton);

examples/flutter_gallery/test/smoke_test.dart

@@ -96,7 +96,7 @@ Future<Null> smokeDemo(WidgetTester tester, GalleryDemo demo) async {
 }
 
 Future<Null> smokeOptionsPage(WidgetTester tester) async {
-  final Finder showOptionsPageButton = find.byTooltip('Show options page');
+  final Finder showOptionsPageButton = find.byTooltip('Toggle options page');
 
   // Show the options page
   await tester.tap(showOptionsPageButton);