[web] Do not reset 'cursor' in PersistedPlatformView. (flutter#22977)

Author: ditman

lib/web_ui/dev/README.md

@@ -165,3 +165,17 @@ Some useful links:
 2. Browser and driver CIPD [packages](https://chrome-infra-packages.appspot.com/p/flutter_internal) (Note: Access rights are restricted for these packages.)
 3. LUCI web [recipe](https://flutter.googlesource.com/recipes/+/refs/heads/master/recipes/web_engine.py)
 4. More general reading on CIPD packages [link](https://chromium.googlesource.com/chromium/src.git/+/master/docs/cipd.md#What-is-CIPD)
+
+## Troubleshooting
+
+### Can't load Kernel binary: Invalid kernel binary format version.
+
+Some times `.dart_tool` cache invalidation fails, and you'll end up with a cached version of `felt` that is not compatible with the Dart SDK that you're using.
+
+In that case, any invocation to `felt` will fail with:
+
+`Can't load Kernel binary: Invalid kernel binary format version.`
+
+The solution is to delete the cached `felt.snapshot` files within `engine/src/flutter/lib/web_ui`:
+
+**`rm .dart_tool/felt.snapshot*`**

lib/web_ui/lib/src/engine/html/platform_view.dart

@@ -44,6 +44,7 @@ class PersistedPlatformView extends PersistedLeafSurface {
     _styleReset.innerHtml = '''
       :host {
         all: initial;
+        cursor: inherit;
       }''';
     _shadowRoot.append(_styleReset);
     final html.Element? platformView =

lib/web_ui/test/engine/surface/platform_view_test.dart

@@ -67,6 +67,18 @@ void testMain() {
         expect(view.canUpdateAsMatch(anyView), isFalse);
       });
     });
+
+    group('createElement', () {
+      test('adds reset to stylesheet', () {
+        final element = view.createElement();
+        _assertShadowRootStylesheetContains(element, 'all: initial;');
+      });
+
+      test('creates element transparent to "cursor" property', () {
+        final element = view.createElement();
+        _assertShadowRootStylesheetContains(element, 'cursor: inherit;');
+      });
+    });
   });
 }
 
@@ -86,3 +98,14 @@ Future<void> _createPlatformView(int id, String viewType) {
   );
   return completer.future;
 }
+
+void _assertShadowRootStylesheetContains(html.Element element, String rule) {
+  final shadow = element.shadowRoot;
+
+  expect(shadow, isNotNull);
+
+  final html.StyleElement style = shadow.children.first;
+
+  expect(style, isNotNull);
+  expect(style.innerHtml, contains(rule));
+}