A bunch of cleanups and a missing `ShortcutRegistar` in `WidgetsApp` (#104560)

A bunch of random cleanup things I found while doing MenuBar development.

Changes an if test to an assert in binding.dart, since the if should always be true.
Adds the default ShortcutRegistrar that should have been in the ShortcutRegistry PR.
Moves a debug message in the FocusManager to print the result after the focus change instead of before.
Reorders the test parameters in theme_data_test.dart to match the order of the theme data fields everywhere else.

packages/flutter/lib/src/gestures/binding.dart

@@ -399,9 +399,9 @@ mixin GestureBinding on BindingBase implements HitTestable, HitTestDispatcher, H
   @pragma('vm:notify-debugger-on-exception')
   void dispatchEvent(PointerEvent event, HitTestResult? hitTestResult) {
     assert(!locked);
-    // No hit test information implies that this is a [PointerHoverEvent],
-    // [PointerAddedEvent], or [PointerRemovedEvent]. These events are specially
-    // routed here; other events will be routed through the `handleEvent` below.
+    // No hit test information implies that this is a [PointerAddedEvent] or
+    // [PointerRemovedEvent]. These events are specially routed here; other
+    // events will be routed through the `handleEvent` below.
     if (hitTestResult == null) {
       assert(event is PointerAddedEvent || event is PointerRemovedEvent);
       try {

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

@@ -1730,7 +1730,9 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
               actions: widget.actions ?? WidgetsApp.defaultActions,
               child: FocusTraversalGroup(
                 policy: ReadingOrderTraversalPolicy(),
-                child: child,
+                child: ShortcutRegistrar(
+                  child: child,
+                ),
               ),
             ),
           ),

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

@@ -1798,10 +1798,10 @@ class FocusManager with DiagnosticableTreeMixin, ChangeNotifier {
         _dirtyNodes.add(_primaryFocus!);
       }
     }
-    assert(_focusDebug('Notifying ${_dirtyNodes.length} dirty nodes:', _dirtyNodes.toList().map<String>((FocusNode node) => node.toString())));
     for (final FocusNode node in _dirtyNodes) {
       node._notify();
     }
+    assert(_focusDebug('Notified ${_dirtyNodes.length} dirty nodes:', _dirtyNodes.toList().map<String>((FocusNode node) => node.toString())));
     _dirtyNodes.clear();
     if (previousFocus != _primaryFocus) {
       notifyListeners();

packages/flutter/test/material/debug_test.dart

@@ -186,6 +186,13 @@ void main() {
       '     Localizations\n'
       '     MediaQuery\n'
       '     _MediaQueryFromWindow\n'
+      '     _ShortcutRegistrarMarker\n'
+      '     _ShortcutsMarker\n'
+      '     Semantics\n'
+      '     _FocusMarker\n'
+      '     Focus\n'
+      '     Shortcuts\n'
+      '     ShortcutRegistrar\n'
       '     _FocusMarker\n'
       '     Focus\n'
       '     _FocusTraversalGroupMarker\n'

packages/flutter/test/widgets/focus_manager_test.dart

@@ -1697,7 +1697,7 @@ void main() {
     final String messagesStr = messages.toString();
     expect(messagesStr.split('\n').length, equals(58));
     expect(messagesStr, contains(RegExp(r'   └─Child 1: FocusScopeNode#[a-f0-9]{5}\(parent1 \[PRIMARY FOCUS\]\)')));
-    expect(messagesStr, contains('FOCUS: Notifying 2 dirty nodes'));
+    expect(messagesStr, contains('FOCUS: Notified 2 dirty nodes'));
     expect(messagesStr, contains(RegExp(r'FOCUS: Scheduling update, current focus is null, next focus will be FocusScopeNode#.*parent1')));
   });
 }

packages/flutter/test/widgets/shortcuts_test.dart

@@ -1354,6 +1354,51 @@ void main() {
       expect(invokedB, equals(1));
     });
 
+    testWidgets('MaterialApp has a ShortcutRegistrar listening', (WidgetTester tester) async {
+      int invokedA = 0;
+      int invokedB = 0;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: TestCallbackRegistration(
+            shortcuts: <ShortcutActivator, Intent>{
+              const SingleActivator(LogicalKeyboardKey.keyA): VoidCallbackIntent(() {
+                invokedA += 1;
+              }),
+              const SingleActivator(LogicalKeyboardKey.keyB): VoidCallbackIntent(() {
+                invokedB += 1;
+              }),
+            },
+            child: Actions(
+              actions: <Type, Action<Intent>>{
+                VoidCallbackIntent: VoidCallbackAction(),
+              },
+              child: const Focus(
+                autofocus: true,
+                child: Placeholder(),
+              ),
+            ),
+          ),
+        ),
+      );
+      await tester.pump();
+
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.keyA);
+      await tester.pump();
+      expect(invokedA, equals(1));
+      expect(invokedB, equals(0));
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.keyA);
+      expect(invokedA, equals(1));
+      expect(invokedB, equals(0));
+      invokedA = 0;
+      invokedB = 0;
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.keyB);
+      expect(invokedA, equals(0));
+      expect(invokedB, equals(1));
+      await tester.sendKeyUpEvent(LogicalKeyboardKey.keyB);
+      expect(invokedA, equals(0));
+      expect(invokedB, equals(1));
+    });
+
     testWidgets("doesn't override text field shortcuts", (WidgetTester tester) async {
       final TextEditingController controller = TextEditingController();
       await tester.pumpWidget(