Fix inconsistent enum/class private member naming (#32409)

Classes that model enums in dart:ui typically name fields modelling the
enum values as `_kFooIndex`. This associated value matches the enum
value from embedder.h.

In https://github.com/flutter/engine/pull/32408 we add a test that
verifies that dart:ui classes model the same set of values in the native
implementation, the web_ui implementation, and the embedder API. Testing
this is much simpler if we use consistent naming for all enum values.

Issue: https://github.com/flutter/engine/pull/32408
diff --git a/lib/ui/semantics.dart b/lib/ui/semantics.dart
index 6e4589d..301b920 100644
--- a/lib/ui/semantics.dart
+++ b/lib/ui/semantics.dart
@@ -34,11 +34,11 @@
   static const int _kPasteIndex = 1 << 14;
   static const int _kDidGainAccessibilityFocusIndex = 1 << 15;
   static const int _kDidLoseAccessibilityFocusIndex = 1 << 16;
-  static const int _kCustomAction = 1 << 17;
+  static const int _kCustomActionIndex = 1 << 17;
   static const int _kDismissIndex = 1 << 18;
   static const int _kMoveCursorForwardByWordIndex = 1 << 19;
   static const int _kMoveCursorBackwardByWordIndex = 1 << 20;
-  static const int _kSetText = 1 << 21;
+  static const int _kSetTextIndex = 1 << 21;
   // READ THIS: if you add an action here, you MUST update the
   // numSemanticsActions value in testing/dart/semantics_test.dart, or tests
   // will fail.
@@ -122,7 +122,7 @@
   ///
   /// The action includes a string argument, which is the new text to
   /// replace.
-  static const SemanticsAction setText = SemanticsAction._(_kSetText);
+  static const SemanticsAction setText = SemanticsAction._(_kSetTextIndex);
 
   /// Set the text selection to the given range.
   ///
@@ -174,7 +174,7 @@
   ///
   /// This handler is added automatically whenever a custom accessibility
   /// action is added to a semantics node.
-  static const SemanticsAction customAction = SemanticsAction._(_kCustomAction);
+  static const SemanticsAction customAction = SemanticsAction._(_kCustomActionIndex);
 
   /// A request that the node should be dismissed.
   ///
@@ -223,11 +223,11 @@
     _kPasteIndex: paste,
     _kDidGainAccessibilityFocusIndex: didGainAccessibilityFocus,
     _kDidLoseAccessibilityFocusIndex: didLoseAccessibilityFocus,
-    _kCustomAction: customAction,
+    _kCustomActionIndex: customAction,
     _kDismissIndex: dismiss,
     _kMoveCursorForwardByWordIndex: moveCursorForwardByWord,
     _kMoveCursorBackwardByWordIndex: moveCursorBackwardByWord,
-    _kSetText: setText,
+    _kSetTextIndex: setText,
   };
 
   @override
@@ -267,7 +267,7 @@
         return 'SemanticsAction.didGainAccessibilityFocus';
       case _kDidLoseAccessibilityFocusIndex:
         return 'SemanticsAction.didLoseAccessibilityFocus';
-      case _kCustomAction:
+      case _kCustomActionIndex:
         return 'SemanticsAction.customAction';
       case _kDismissIndex:
         return 'SemanticsAction.dismiss';
@@ -275,7 +275,7 @@
         return 'SemanticsAction.moveCursorForwardByWord';
       case _kMoveCursorBackwardByWordIndex:
         return 'SemanticsAction.moveCursorBackwardByWord';
-      case _kSetText:
+      case _kSetTextIndex:
         return 'SemanticsAction.setText';
     }
     assert(false, 'Unhandled index: $index (0x${index.toRadixString(8).padLeft(4, "0")})');
diff --git a/lib/ui/window.dart b/lib/ui/window.dart
index 8af7d49..0d92491 100644
--- a/lib/ui/window.dart
+++ b/lib/ui/window.dart
@@ -786,7 +786,7 @@
 class AccessibilityFeatures {
   const AccessibilityFeatures._(this._index);
 
-  static const int _kAccessibleNavigation = 1 << 0;
+  static const int _kAccessibleNavigationIndex = 1 << 0;
   static const int _kInvertColorsIndex = 1 << 1;
   static const int _kDisableAnimationsIndex = 1 << 2;
   static const int _kBoldTextIndex = 1 << 3;
@@ -801,7 +801,7 @@
   /// interaction model of the device.
   ///
   /// For example, TalkBack on Android and VoiceOver on iOS enable this flag.
-  bool get accessibleNavigation => _kAccessibleNavigation & _index != 0;
+  bool get accessibleNavigation => _kAccessibleNavigationIndex & _index != 0;
 
   /// The platform is inverting the colors of the application.
   bool get invertColors => _kInvertColorsIndex & _index != 0;
diff --git a/lib/web_ui/lib/semantics.dart b/lib/web_ui/lib/semantics.dart
index ab18cea..8e94951 100644
--- a/lib/web_ui/lib/semantics.dart
+++ b/lib/web_ui/lib/semantics.dart
@@ -24,11 +24,11 @@
   static const int _kPasteIndex = 1 << 14;
   static const int _kDidGainAccessibilityFocusIndex = 1 << 15;
   static const int _kDidLoseAccessibilityFocusIndex = 1 << 16;
-  static const int _kCustomAction = 1 << 17;
+  static const int _kCustomActionIndex = 1 << 17;
   static const int _kDismissIndex = 1 << 18;
   static const int _kMoveCursorForwardByWordIndex = 1 << 19;
   static const int _kMoveCursorBackwardByWordIndex = 1 << 20;
-  static const int _kSetText = 1 << 21;
+  static const int _kSetTextIndex = 1 << 21;
 
   final int index;
 
@@ -43,14 +43,14 @@
   static const SemanticsAction showOnScreen = SemanticsAction._(_kShowOnScreenIndex);
   static const SemanticsAction moveCursorForwardByCharacter = SemanticsAction._(_kMoveCursorForwardByCharacterIndex);
   static const SemanticsAction moveCursorBackwardByCharacter = SemanticsAction._(_kMoveCursorBackwardByCharacterIndex);
-  static const SemanticsAction setText = SemanticsAction._(_kSetText);
+  static const SemanticsAction setText = SemanticsAction._(_kSetTextIndex);
   static const SemanticsAction setSelection = SemanticsAction._(_kSetSelectionIndex);
   static const SemanticsAction copy = SemanticsAction._(_kCopyIndex);
   static const SemanticsAction cut = SemanticsAction._(_kCutIndex);
   static const SemanticsAction paste = SemanticsAction._(_kPasteIndex);
   static const SemanticsAction didGainAccessibilityFocus = SemanticsAction._(_kDidGainAccessibilityFocusIndex);
   static const SemanticsAction didLoseAccessibilityFocus = SemanticsAction._(_kDidLoseAccessibilityFocusIndex);
-  static const SemanticsAction customAction = SemanticsAction._(_kCustomAction);
+  static const SemanticsAction customAction = SemanticsAction._(_kCustomActionIndex);
   static const SemanticsAction dismiss = SemanticsAction._(_kDismissIndex);
   static const SemanticsAction moveCursorForwardByWord = SemanticsAction._(_kMoveCursorForwardByWordIndex);
   static const SemanticsAction moveCursorBackwardByWord = SemanticsAction._(_kMoveCursorBackwardByWordIndex);
@@ -73,11 +73,11 @@
     _kPasteIndex: paste,
     _kDidGainAccessibilityFocusIndex: didGainAccessibilityFocus,
     _kDidLoseAccessibilityFocusIndex: didLoseAccessibilityFocus,
-    _kCustomAction: customAction,
+    _kCustomActionIndex: customAction,
     _kDismissIndex: dismiss,
     _kMoveCursorForwardByWordIndex: moveCursorForwardByWord,
     _kMoveCursorBackwardByWordIndex: moveCursorBackwardByWord,
-    _kSetText: setText,
+    _kSetTextIndex: setText,
   };
 
   @override
@@ -117,7 +117,7 @@
         return 'SemanticsAction.didGainAccessibilityFocus';
       case _kDidLoseAccessibilityFocusIndex:
         return 'SemanticsAction.didLoseAccessibilityFocus';
-      case _kCustomAction:
+      case _kCustomActionIndex:
         return 'SemanticsAction.customAction';
       case _kDismissIndex:
         return 'SemanticsAction.dismiss';
@@ -125,7 +125,7 @@
         return 'SemanticsAction.moveCursorForwardByWord';
       case _kMoveCursorBackwardByWordIndex:
         return 'SemanticsAction.moveCursorBackwardByWord';
-      case _kSetText:
+      case _kSetTextIndex:
         return 'SemanticsAction.setText';
     }
     assert(false, 'Unhandled index: $index (0x${index.toRadixString(8).padLeft(4, "0")})');