Another fix incremental constants - annotations should use the old unit element.

pkg/analyzer/lib/src/task/incremental_element_builder.dart

Index: pkg/analyzer/lib/src/task/incremental_element_builder.dart
diff --git a/pkg/analyzer/lib/src/task/incremental_element_builder.dart b/pkg/analyzer/lib/src/task/incremental_element_builder.dart
index abd306798383df8b047545d96ef73893ad5249ce..d20ce0bbc37e97abb74d04e1072ca9e05ad5e558 100644
--- a/pkg/analyzer/lib/src/task/incremental_element_builder.dart
+++ b/pkg/analyzer/lib/src/task/incremental_element_builder.dart
@@ -163,6 +163,12 @@ class IncrementalCompilationUnitElementBuilder {
         new ConstantFinder(unitElement.context, unitSource, librarySource);
     oldUnit.accept(finder);
     unitConstants.addAll(finder.constantsToCompute);
+    // Update annotation constants to using the old unit element.
+    for (ConstantEvaluationTarget constant in unitConstants) {
+      if (constant is ElementAnnotationImpl) {
+        constant.compilationUnit = unitElement;
+      }
+    }
   }
 
   ClassElementDelta _processClassMembers(