Get the most basic mixin applications working.

sdk/lib/_internal/compiler/implementation/elements/elements.dart

Index: sdk/lib/_internal/compiler/implementation/elements/elements.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/elements.dart b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
index b9f9c51a107b954d6396f05cead5d6b154cc627d..101a6ca9d55b8537eedd914a6005813f6cdd231b 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/elements.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
@@ -639,6 +639,7 @@ abstract class ClassElement extends TypeDeclarationElement
   int get resolutionState;
   SourceString get nativeTagInfo;
 
+  bool get isMixinApplication;
   bool get hasBackendMembers;
   bool get hasLocalScopeMembers;
 
@@ -670,6 +671,12 @@ abstract class ClassElement extends TypeDeclarationElement
   void addMember(Element element, DiagnosticListener listener);
   void addToScope(Element element, DiagnosticListener listener);
 
+  /**
+   * Add a synthetic nullary constructor if there are no other
+   * constructors.
+   */
+  void addDefaultConstructorIfNeeded(Compiler compiler);
+
   void addBackendMember(Element element);
   void reverseBackendMembers();