Add a flag to the element model to identify mixin applications.

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index 926244b5c090a74cbdfd43448b684d4ccdb25d35..70badf4932f4efd8a6116ed7ddb3606ecbdebb83 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -2487,6 +2487,7 @@ class ElementBuilder extends RecursiveAstVisitor<Object> {
     SimpleIdentifier className = node.name;
     ClassElementImpl element = new ClassElementImpl.forNode(className);
     element.abstract = node.abstractKeyword != null;
+    element.mixinApplication = true;
     element.typedef = true;
     List<TypeParameterElement> typeParameters = holder.typeParameters;
     element.typeParameters = typeParameters;