Load patches via callback.

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

Index: sdk/lib/_internal/compiler/implementation/scanner/listener.dart
diff --git a/sdk/lib/_internal/compiler/implementation/scanner/listener.dart b/sdk/lib/_internal/compiler/implementation/scanner/listener.dart
index 3e4be25ecf12ecfcf78d3faaa50d8050cf8aac6d..7a19ce71b06c74dfd712ec88712145a7c1f1fbb7 100644
--- a/sdk/lib/_internal/compiler/implementation/scanner/listener.dart
+++ b/sdk/lib/_internal/compiler/implementation/scanner/listener.dart
@@ -817,9 +817,9 @@ class ElementListener extends Listener {
   bool allowLibraryTags() {
     // Library tags are only allowed in the library file itself, not
     // in sourced files.
-    LibraryElement library = compilationUnitElement.library;
-    return !compilationUnitElement.hasMembers
-      && library.entryCompilationUnit == compilationUnitElement;
+    LibraryElement library = compilationUnitElement.implementationLibrary;
+    return !compilationUnitElement.hasMembers &&
+           library.entryCompilationUnit == compilationUnitElement;
   }
 
   void endLibraryName(Token libraryKeyword, Token semicolon) {