Introduces the new syntax for deferred loading

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index d157b569549862ab23235d589406930f0d2b206e..58a10bce0ed049f61a271379d5ede655cc2b8fd5 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -1556,6 +1556,13 @@ class JavaScriptBackend extends Backend {
       mustRetainMetadata = true;
     } else if (element == getIsolateAffinityTagMarker) {
       needToInitializeIsolateAffinityTag = true;
+    } else if (element.isDeferredLoaderFunction()) {
+      // TODO(sigurdm): Create a function registerLoadLibraryAccess.
+      if (compiler.loadLibraryFunction == null) {
+        compiler.loadLibraryFunction = compiler.findHelper("_load");
+        enqueueInResolution(compiler.loadLibraryFunction,
+                            compiler.globalDependencies);
+      }
     }
     customElementsAnalysis.registerStaticUse(element, enqueuer);
   }