Add test case for #19270.

Closes #19270.

Author: sjrd

tests/run/i19270.scala

@@ -0,0 +1,17 @@
+// scalajs: --skip
+
+trait T {
+  def foo(x: Int): Int = x + 1
+}
+
+class C extends T
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println("i19270")
+    val m = classOf[C].getDeclaredMethod("foo", classOf[Int])
+    assert(m.getDeclaringClass() == classOf[C], m.getDeclaringClass())
+    assert(!m.isBridge(), "foo should not have the ACC_BRIDGE flag")
+    assert(!m.isSynthetic(), "foo should not have the ACC_SYNTHETIC flag")
+  }
+}