[skwasm] Fix implementation of SkwasmPath.relativeLineTo (#57201)

Fixes flutter/flutter#157161

Author: jason-simmons

lib/web_ui/lib/src/engine/skwasm/skwasm_impl/path.dart

@@ -50,7 +50,7 @@ class SkwasmPath extends SkwasmObjectWrapper<RawPath> implements ScenePath {
   void lineTo(double x, double y) => pathLineTo(handle, x, y);
 
   @override
-  void relativeLineTo(double x, double y) => pathRelativeMoveTo(handle, x, y);
+  void relativeLineTo(double x, double y) => pathRelativeLineTo(handle, x, y);
 
   @override
   void quadraticBezierTo(double x1, double y1, double x2, double y2) =>

lib/web_ui/test/ui/path_test.dart

@@ -239,4 +239,13 @@ Future<void> testMain() async {
     expect(newFirstMetric.extractPath(4.0, 10.0).computeMetrics().first.length, 6.0);
   // TODO(hterkelsen): isClosed always returns false in the HTML renderer, https://github.com/flutter/flutter/issues/114446
   }, skip: isHtml);
+
+  test('path relativeLineTo', () {
+    final p = Path();
+    p.moveTo(100, 100);
+    p.relativeLineTo(-50, -50);
+    p.relativeLineTo(100, 0);
+    p.relativeLineTo(-50, 50);
+    expect(p.getBounds(), equals(const Rect.fromLTRB(50.0, 50.0, 150.0, 100.0)));
+  });
 }