Add related types check to analyze_dart2js_test

pkg/compiler/lib/src/world.dart

Index: pkg/compiler/lib/src/world.dart
diff --git a/pkg/compiler/lib/src/world.dart b/pkg/compiler/lib/src/world.dart
index b8925b3bbe61dd5abac70488952b7e2516edc109..6cfa45f9700bf74ff7d9ffbc36b8351f07834fe1 100644
--- a/pkg/compiler/lib/src/world.dart
+++ b/pkg/compiler/lib/src/world.dart
@@ -89,6 +89,9 @@ abstract class ClassWorld {
   /// including [cls] if it is live.
   Iterable<ClassElement> strictSubtypesOf(ClassElement cls);
 
+  /// Returns `true` if [a] and [b] have any known common subtypes.
+  bool haveAnyCommonSubtypes(ClassElement a, ClassElement b);
+
   /// Returns `true` if any live class other than [cls] extends [cls].
   bool hasAnyStrictSubclass(ClassElement cls);
 
@@ -216,6 +219,21 @@ class World implements ClassWorld {
     }
   }
 
+  /// Returns `true` if [a] and [b] have any known common subtypes.
+  bool haveAnyCommonSubtypes(ClassElement a, ClassElement b) {
+    ClassSet classSetA = _classSets[a.declaration];
+    ClassSet classSetB = _classSets[b.declaration];
+    if (classSetA == null || classSetB == null) return false;
+    // TODO(johnniwinther): Implement an optimized query on [ClassSet].
+    Set<ClassElement> subtypesOfB = classSetB.subtypes().toSet();
+    for (ClassElement subtypeOfA in classSetA.subtypes()) {
+      if (subtypesOfB.contains(subtypeOfA)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   /// Returns `true` if any directly instantiated class other than [cls] extends
   /// [cls].
   bool hasAnyStrictSubclass(ClassElement cls) {