Let Backend determine support for deferred loading.

pkg/compiler/lib/src/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 296 matching lines @@
   void onResolutionComplete() {}
   void onTypeInferenceComplete() {}
 
   ItemCompilationContext createItemCompilationContext() {
     return new ItemCompilationContext();
   }
 
   bool classNeedsRti(ClassElement cls);
   bool methodNeedsRti(FunctionElement function);
 
+  /// Register deferred loading. Returns `true` if the backend supports deferred
+  /// loading.
+  bool registerDeferredLoading(Spannable node, Registry registry);
+
   /// Called during codegen when [constant] has been used.
   void registerCompileTimeConstant(ConstantValue constant, Registry registry) {}
 
   /// Called during resolution when a constant value for [metadata] on
   /// [annotatedElement] has been evaluated.
   void registerMetadataConstant(MetadataAnnotation metadata,
                                 Element annotatedElement,
                                 Registry registry) {}
 
   /// Called to notify to the backend that a class is being instantiated.
@@ skipping 2133 matching lines @@
     return futureClass.computeType(compiler).createInstantiation([elementType]);
   }
 
   @override
   InterfaceType streamType([DartType elementType = const DynamicType()]) {
     return streamClass.computeType(compiler).createInstantiation([elementType]);
   }
 }
 
 typedef void InternalErrorFunction(Spannable location, String message);