Tiny improve code style by using records instead of lists (flutter#135886)

Author: fzyzcjy

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

@@ -1025,7 +1025,7 @@ class SelectionOverlay {
         context: context,
         below: magnifierConfiguration.shouldDisplayHandlesInMagnifier
             ? null
-            : _handles?.first,
+            : _handles?.start,
         builder: (_) => builtMagnifier);
   }
 
@@ -1333,7 +1333,7 @@ class SelectionOverlay {
 
   /// A pair of handles. If this is non-null, there are always 2, though the
   /// second is hidden when the selection is collapsed.
-  List<OverlayEntry>? _handles;
+  ({OverlayEntry start, OverlayEntry end})? _handles;
 
   /// A copy/paste toolbar.
   OverlayEntry? _toolbar;
@@ -1351,22 +1351,23 @@ class SelectionOverlay {
       return;
     }
 
-    _handles = <OverlayEntry>[
-      OverlayEntry(builder: _buildStartHandle),
-      OverlayEntry(builder: _buildEndHandle),
-    ];
-    Overlay.of(context, rootOverlay: true, debugRequiredFor: debugRequiredFor).insertAll(_handles!);
+    _handles = (
+      start: OverlayEntry(builder: _buildStartHandle),
+      end: OverlayEntry(builder: _buildEndHandle),
+    );
+    Overlay.of(context, rootOverlay: true, debugRequiredFor: debugRequiredFor)
+        .insertAll(<OverlayEntry>[_handles!.start, _handles!.end]);
   }
 
   /// {@template flutter.widgets.SelectionOverlay.hideHandles}
   /// Destroys the handles by removing them from overlay.
   /// {@endtemplate}
   void hideHandles() {
     if (_handles != null) {
-      _handles![0].remove();
-      _handles![0].dispose();
-      _handles![1].remove();
-      _handles![1].dispose();
+      _handles!.start.remove();
+      _handles!.start.dispose();
+      _handles!.end.remove();
+      _handles!.end.dispose();
       _handles = null;
     }
   }
@@ -1444,8 +1445,8 @@ class SelectionOverlay {
       SchedulerBinding.instance.addPostFrameCallback((Duration duration) {
         _buildScheduled = false;
         if (_handles != null) {
-          _handles![0].markNeedsBuild();
-          _handles![1].markNeedsBuild();
+          _handles!.start.markNeedsBuild();
+          _handles!.end.markNeedsBuild();
         }
         _toolbar?.markNeedsBuild();
         if (_contextMenuController.isShown) {
@@ -1456,8 +1457,8 @@ class SelectionOverlay {
       });
     } else {
       if (_handles != null) {
-        _handles![0].markNeedsBuild();
-        _handles![1].markNeedsBuild();
+        _handles!.start.markNeedsBuild();
+        _handles!.end.markNeedsBuild();
       }
       _toolbar?.markNeedsBuild();
       if (_contextMenuController.isShown) {
@@ -1474,10 +1475,10 @@ class SelectionOverlay {
   void hide() {
     _magnifierController.hide();
     if (_handles != null) {
-      _handles![0].remove();
-      _handles![0].dispose();
-      _handles![1].remove();
-      _handles![1].dispose();
+      _handles!.start.remove();
+      _handles!.start.dispose();
+      _handles!.end.remove();
+      _handles!.end.dispose();
       _handles = null;
     }
     if (_toolbar != null || _contextMenuController.isShown || _spellCheckToolbarController.isShown) {