Issue 6770. Support for @deprecated on library directive.

compiler/java/com/google/dart/compiler/ast/LibraryUnit.java

Index: compiler/java/com/google/dart/compiler/ast/LibraryUnit.java
diff --git a/compiler/java/com/google/dart/compiler/ast/LibraryUnit.java b/compiler/java/com/google/dart/compiler/ast/LibraryUnit.java
index d6e2a3153b2d3b33c7ded6cc0856aef82926d951..2bd491fbdbb2345b17354b356ccfb61b4558c927 100644
--- a/compiler/java/com/google/dart/compiler/ast/LibraryUnit.java
+++ b/compiler/java/com/google/dart/compiler/ast/LibraryUnit.java
@@ -187,6 +187,14 @@ public class LibraryUnit {
 
   public void setSelfDartUnit(DartUnit unit) {
     this.selfDartUnit = unit;
+    // set DartObsoleteMetadata for LibraryElement
+    if (unit != null) {
+      List<DartDirective> directives = unit.getDirectives();
+      if (!directives.isEmpty() && directives.get(0) instanceof DartLibraryDirective) {
+        DartLibraryDirective libraryDirective = (DartLibraryDirective) directives.get(0);
+        Elements.setLibraryMetadata(element, libraryDirective.getObsoleteMetadata());
+      }
+    }
   }
 
   /**