Extract ResolutionWorldBuilderBase from ElementResolutionWorldBuilder

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 2a2fa48bc45a34892563049b25d2bbf3b0838c3b..68df7fd2dc5d733419fdbdf6ae10b851f14be2be 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -1894,12 +1894,12 @@ class _CompilerElementEnvironment implements ElementEnvironment {
   }
 
   @override
-  ClassEntity getSuperClass(ClassElement cls) {
-    cls = cls.superclass;
-    while (cls != null && cls.isUnnamedMixinApplication) {
-      cls = cls.superclass;
-    }
-    return cls;
+  ClassEntity getSuperClass(ClassElement cls) => cls.superclass;
+
+  @override
+  void forEachSupertype(
+      ClassElement cls, void f(ResolutionInterfaceType supertype)) {
+    cls.allSupertypes.forEach((ResolutionDartType supertype) => f(supertype));
   }
 
   @override