Add test for ambiguation of related prototype & instance props

This case seems to work correctly but is not covered in AmbiguatePropertiesTest.

PiperOrigin-RevId: 322079970

Author: lauraharker

test/com/google/javascript/jscomp/AmbiguatePropertiesTest.java

@@ -1249,6 +1249,48 @@ public void testGenericPrototypeObject() {
     test(js, output);
   }
 
+  @Test
+  public void testRelatedInstanceAndPrototypePropNotAmbiguated() {
+    test(
+        lines(
+            "class Foo {", //
+            "  constructor() {",
+            "    this.y = 0;",
+            "  }",
+            "  x() {}",
+            "}"),
+        lines(
+            "class Foo {", //
+            "  constructor() {",
+            "    this.b = 0;",
+            "  }",
+            "  a() {}",
+            "}"));
+  }
+
+  @Test
+  public void testRelatedInstanceAndSuperclassPrototypePropNotAmbiguated() {
+    test(
+        lines(
+            "class Foo {", //
+            "  x() {}",
+            "}",
+            "class Bar extends Foo {",
+            "  constructor() {",
+            "    this.y = 0;",
+            "  }",
+            "}"),
+        lines(
+            "class Foo {", //
+            "  a() {}",
+            "}",
+            "class Bar extends Foo {",
+            "  constructor() {",
+            "    this.b = 0;",
+            "  }",
+            "}"));
+  }
+
   @Test
   public void testPropertiesWithTypesThatHaveBeenNarrowed() {
     String js = lines(