Issue dartdoc#1124. Get used elements from directive comments.

pkg/analyzer/test/generated/hint_code_test.dart

Index: pkg/analyzer/test/generated/hint_code_test.dart
diff --git a/pkg/analyzer/test/generated/hint_code_test.dart b/pkg/analyzer/test/generated/hint_code_test.dart
index 536553bb74ac4255909f0a471d153f3e6d66a9c6..735fc78b33893a92dfcdb3c1d56dba06d64c04d3 100644
--- a/pkg/analyzer/test/generated/hint_code_test.dart
+++ b/pkg/analyzer/test/generated/hint_code_test.dart
@@ -2709,6 +2709,15 @@ class A {}''');
     verify([source, source2]);
   }
 
+  void test_unusedImport_inComment_libraryDirective() {
+    Source source = addSource(r'''
+/// Use [Future] class.
+library L;
+import 'dart:async';
+''');
+    assertNoErrors(source);
+  }
+
   void test_unusedImport_show() {
     Source source = addSource(r'''
 library L;