Check for using 'this' and 'super'. Tests. Issue 662.

compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java

Index: compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java b/compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java
index 344aca980f116eedb1fd35bf4450aff3d1990cad..f0a5feeab51b2787f7d39bd7be6111ebf4c7dabe 100644
--- a/compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java
+++ b/compiler/java/com/google/dart/compiler/resolver/MemberBuilder.java
@@ -36,13 +36,14 @@ public class MemberBuilder {
   private LibraryElement libraryElement;
 
   public void exec(DartUnit unit, DartCompilerContext context, CoreTypeProvider typeProvider) {
-    libraryElement = unit.getLibrary().getElement();
-    exec(unit, context, libraryElement.getScope(), typeProvider);
+    Scope scope = unit.getLibrary().getElement().getScope();
+    exec(unit, context, scope, typeProvider);
   }
 
   @VisibleForTesting
   public void exec(DartUnit unit, DartCompilerContext compilerContext, Scope scope,
                    CoreTypeProvider typeProvider) {
+    libraryElement = unit.getLibrary().getElement();
     topLevelContext = new ResolutionContext(scope, compilerContext, typeProvider);
     unit.accept(new MemberElementBuilder(typeProvider));
   }