[dart2dart] Fix assertions for tests to pass in checked mode.

BUG=5819

Review URL: https://codereview.chromium.org//11108014

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@13622 260f80e4-7a28-3924-810f-c04153c831b5
diff --git a/lib/compiler/implementation/dart_backend/placeholder_collector.dart b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
index 381b5da..6e815c1 100644
--- a/lib/compiler/implementation/dart_backend/placeholder_collector.dart
+++ b/lib/compiler/implementation/dart_backend/placeholder_collector.dart
@@ -394,7 +394,10 @@
       if (send.receiver !== null) tryMakeMemberPlaceholder(send.selector);
     } else if (!element.isErroneous()) {
       if (Elements.isStaticOrTopLevel(element)) {
-        assert(element is VariableElement || element.isAccessor());
+        // TODO(smok): Worth investigating why sometimes we get getter/setter
+        // here and sometimes abstract field.
+        assert(element is VariableElement || element.isAccessor()
+            || element.isAbstractField() || element.isFunction());
         makeElementPlaceholder(send.selector, element);
       } else {
         assert(send.selector is Identifier);