Add StaticUse for more precise registration of statically known element use.

pkg/compiler/lib/src/deferred_load.dart

Index: pkg/compiler/lib/src/deferred_load.dart
diff --git a/pkg/compiler/lib/src/deferred_load.dart b/pkg/compiler/lib/src/deferred_load.dart
index fbc547cb53445a9635685541e392ed4ee17061b7..ab4f1cad961ce585453b5ebe6636f775a580bc51 100644
--- a/pkg/compiler/lib/src/deferred_load.dart
+++ b/pkg/compiler/lib/src/deferred_load.dart
@@ -47,6 +47,8 @@ import 'tree/tree.dart' show
     LiteralString,
     NewExpression,
     Node;
+import 'universe/use.dart' show
+    StaticUse;
 import 'universe/world_impact.dart' show
     WorldImpact;
 import 'util/setlet.dart' show
@@ -312,7 +314,9 @@ class DeferredLoadTask extends CompilerTask {
 
         WorldImpact worldImpact =
             compiler.resolution.getWorldImpact(analyzableElement);
-        elements.addAll(worldImpact.staticUses);
+        worldImpact.staticUses.forEach((StaticUse staticUse) {
+          elements.add(staticUse.element);
+        });
         elements.addAll(worldImpact.closures);
         for (DartType type in worldImpact.typeLiterals) {
           if (type.isTypedef || type.isInterfaceType) {