Refactor LoopHandler to avoid calling KernelAstAdapter.getNode

pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart

Index: pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
index 4b8ff757640eeb5e6cc7b27f6c68e84a286177da..4afcbc4e0e69fa2dec4bd94e513e699c7a69a476 100644
--- a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
@@ -277,6 +277,12 @@ class KernelToLocalsMapImpl implements KernelToLocalsMap {
       return new KLocal(node.name, currentMember);
     });
   }
+
+  @override
+  LoopClosureRepresentationInfo getClosureRepresentationInfoForLoop(
+      ClosureClassMaps closureClassMaps, ir.TreeNode node) {
+    return const LoopClosureRepresentationInfo();
+  }
 }
 
 class KLocal implements Local {