Reverts "Set stable color for semantics debugger (#157884)" (#159354)

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Reverts: flutter/flutter#157884
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<!-- start_initiating_author -->
Initiated by: chunhtai
<!-- end_initiating_author -->
<!-- start_revert_reason -->
Reason for reverting: merge by mistake
<!-- end_revert_reason -->
<!-- start_original_pr_author -->
Original PR Author: chunhtai
<!-- end_original_pr_author -->

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Reviewed By: {LongCatIsLooong}
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This change reverts the following previous change:
fixes https://github.com/flutter/flutter/issues/156242



## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [ ] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [ ] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.

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on [Discord].

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Co-authored-by: auto-submit[bot] <flutter-engprod-team@google.com>

packages/flutter/lib/src/semantics/semantics.dart

@@ -2092,7 +2092,8 @@ class SemanticsNode with DiagnosticableTreeMixin {
   /// Visits the immediate children of this node.
   ///
   /// This function calls visitor for each immediate child until visitor returns
-  /// false.
+  /// false. Returns true if all the visitor calls returned true, otherwise
+  /// returns false.
   void visitChildren(SemanticsNodeVisitor visitor) {
     if (_children != null) {
       for (final SemanticsNode child in _children!) {

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

@@ -202,7 +202,7 @@ class _SemanticsDebuggerPainter extends CustomPainter {
     canvas.save();
     canvas.scale(1.0 / devicePixelRatio, 1.0 / devicePixelRatio);
     if (rootNode != null) {
-      _paint(canvas, rootNode, _findDepth(rootNode), 0, 0);
+      _paint(canvas, rootNode, _findDepth(rootNode));
     }
     if (pointerPosition != null) {
       final Paint paint = Paint();
@@ -332,14 +332,14 @@ class _SemanticsDebuggerPainter extends CustomPainter {
     return childrenDepth + 1;
   }
 
-  void _paint(Canvas canvas, SemanticsNode node, int rank, int indexInParent, int level) {
+  void _paint(Canvas canvas, SemanticsNode node, int rank) {
     canvas.save();
     if (node.transform != null) {
       canvas.transform(node.transform!.storage);
     }
     final Rect rect = node.rect;
     if (!rect.isEmpty) {
-      final Color lineColor = _colorForNode(indexInParent, level);
+      final Color lineColor = Color(0xFF000000 + math.Random(node.id).nextInt(0xFFFFFF));
       final Rect innerRect = rect.deflate(rank * 1.0);
       if (innerRect.isEmpty) {
         final Paint fill = Paint()
@@ -361,31 +361,13 @@ class _SemanticsDebuggerPainter extends CustomPainter {
     }
     if (!node.mergeAllDescendantsIntoThisNode) {
       final int childRank = rank - 1;
-      final int childLevel = level + 1;
-      int childIndex = 0;
       node.visitChildren((SemanticsNode child) {
-        _paint(canvas, child, childRank, childIndex, childLevel);
-        childIndex += 1;
+        _paint(canvas, child, childRank);
         return true;
       });
     }
     canvas.restore();
   }
-
-  static Color _colorForNode(int index, int level) {
-    return HSLColor.fromAHSL(
-      1.0,
-      // Use custom hash to ensure stable value regardless of Dart changes
-      360.0 * math.Random(_getColorSeed(index, level)).nextDouble(),
-      1.0,
-      0.7,
-    ).toColor();
-  }
-
-  static int _getColorSeed(int level, int index) {
-    // Should be no collision as long as children number < 10000.
-    return level * 10000 + index;
-  }
 }
 
 /// A widget ignores pointer event but still keeps semantics actions.

packages/flutter/test/widgets/semantics_debugger_test.dart

@@ -61,26 +61,6 @@ void main() {
     expect(true, isTrue); // expect that we reach here without crashing
   });
 
-  testWidgets('SemanticsDebugger draw persistent color based on structure', (WidgetTester tester) async {
-    await tester.pumpWidget(
-      Directionality(
-        textDirection: TextDirection.ltr,
-        child: SemanticsDebugger(
-          child: Stack(
-            children: <Widget>[
-              Semantics(
-                container: true,
-                child: Semantics(container: true),
-              ),
-            ],
-          ),
-        ),
-      ),
-    );
-
-    expect(find.byType(SemanticsDebugger), paints..rect()..rect(color: const Color(0xFFF866FF)));
-  });
-
   testWidgets('SemanticsDebugger reparents subtree', (WidgetTester tester) async {
     final GlobalKey key = GlobalKey();