Clean up deferred checks in Kernel.

pkg/compiler/lib/src/ssa/builder_kernel.dart

 // Copyright (c) 2016, 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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/names.dart';
@@ skipping 578 matching lines @@
       return classMap.callElement;
     }
     Element element = astAdapter.getElement(target);
     return element;
   }
 
   @override
   void visitCheckLibraryIsLoaded(ir.CheckLibraryIsLoaded checkLoad) {
     HInstruction prefixConstant = graph.addConstantString(
         new DartString.literal(checkLoad.import.name), closedWorld);
+    var prefixElement = astAdapter.getElement(checkLoad.import);
     HInstruction uriConstant = graph.addConstantString(
-        new DartString.literal(compiler.deferredLoadTask.getImportDeferName(
-            // TODO(efortuna): Source information.
-            null,
-            astAdapter.getElement(checkLoad.import))),
+        new DartString.literal(prefixElement.deferredImport.uri.toString()),
         closedWorld);
     _pushStaticInvocation(astAdapter.checkDeferredIsLoaded,
         [prefixConstant, uriConstant], astAdapter.checkDeferredIsLoadedType);
   }
 
   @override
   void visitLoadLibrary(ir.LoadLibrary loadLibrary) {
     // TODO(efortuna): Source information!
     push(new HInvokeStatic(
         backend.helpers.loadLibraryWrapper,
@@ skipping 2641 matching lines @@
     enterBlock.setBlockFlow(
         new HTryBlockInformation(
             kernelBuilder.wrapStatementGraph(bodyGraph),
             exception,
             kernelBuilder.wrapStatementGraph(catchGraph),
             kernelBuilder.wrapStatementGraph(finallyGraph)),
         exitBlock);
     kernelBuilder.inTryStatement = previouslyInTryStatement;
   }
 }