Resolve metadata on library tags

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 802214c2d84f0b7e6c4277d95c02490845e9d6dd..843a0624fa2092933fc0a4c852f00ae732ca9658 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -1060,6 +1060,7 @@ abstract class Compiler implements DiagnosticListener {
     // Elements required by enqueueHelpers are global dependencies
     // that are not pulled in by a particular element.
     backend.enqueueHelpers(enqueuer.resolution, globalDependencies);
+    resolveLibraryMetadata();
     processQueue(enqueuer.resolution, main);
     enqueuer.resolution.logSummary(log);
 
@@ -1127,6 +1128,17 @@ abstract class Compiler implements DiagnosticListener {
     }
   }
 
+  // Resolves metadata on library elements.  This is necessary in order to
+  // resolve metadata classes referenced only from metadata on library tags.
+  // TODO(ahe): Figure out how to do this lazily.
+  void resolveLibraryMetadata() {
+    for (LibraryElement library in libraries.values) {
+      for (MetadataAnnotation metadata in library.metadata) {
+        metadata.ensureResolved(this);
+      }
+    }
+  }
+
   void processQueue(Enqueuer world, Element main) {
     world.nativeEnqueuer.processNativeClasses(libraries.values);
     if (main != null) {