Print more layer debug info (#49679)

packages/flutter/lib/src/rendering/layer.dart

@@ -460,6 +460,7 @@ abstract class Layer extends AbstractNode with DiagnosticableTreeMixin {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<Object>('owner', owner, level: parent != null ? DiagnosticLevel.hidden : DiagnosticLevel.info, defaultValue: null));
     properties.add(DiagnosticsProperty<dynamic>('creator', debugCreator, defaultValue: null, level: DiagnosticLevel.debug));
+    properties.add(DiagnosticsProperty<String>('engine layer', describeIdentity(_engineLayer)));
   }
 }
 
@@ -535,6 +536,11 @@ class PictureLayer extends Layer {
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<Rect>('paint bounds', canvasBounds));
+    properties.add(DiagnosticsProperty<String>('picture', describeIdentity(_picture)));
+    properties.add(DiagnosticsProperty<String>(
+      'raster cache hints',
+      'isComplex = $isComplexHint, willChange = $willChangeHint'),
+    );
   }
 
   @override

packages/flutter/test/foundation/service_extensions_test.dart

@@ -270,6 +270,7 @@ void main() {
         r'TransformLayer#[0-9a-f]{5}\n'
         r'   owner: RenderView#[0-9a-f]{5}\n'
         r'   creator: RenderView\n'
+        r'   engine layer: (TransformEngineLayer|PersistedTransform)#[0-9a-f]{5}\n'
         r'   offset: Offset\(0\.0, 0\.0\)\n'
         r'   transform:\n'
         r'     \[0] 3\.0,0\.0,0\.0,0\.0\n'

packages/flutter/test/rendering/layers_test.dart

@@ -256,6 +256,21 @@ void main() {
     );
   });
 
+  test('PictureLayer prints picture, engine layer, and raster cache hints in debug info', () {
+    final PictureRecorder recorder = PictureRecorder();
+    final Canvas canvas = Canvas(recorder);
+    canvas.drawPaint(Paint());
+    final Picture picture = recorder.endRecording();
+    final PictureLayer layer = PictureLayer(const Rect.fromLTRB(0, 0, 1, 1));
+    layer.picture = picture;
+    layer.isComplexHint = true;
+    layer.willChangeHint = false;
+    final List<String> info = _getDebugInfo(layer);
+    expect(info, contains('picture: ${describeIdentity(picture)}'));
+    expect(info, contains('engine layer: ${describeIdentity(null)}'));
+    expect(info, contains('raster cache hints: isComplex = true, willChange = false'));
+  });
+
   test('mutating PictureLayer fields triggers needsAddToScene', () {
     final PictureLayer pictureLayer = PictureLayer(Rect.zero);
     checkNeedsAddToScene(pictureLayer, () {