Separate out ClosureAnalysisInfo to separate interfaces between what

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 db3ab9742a3e1908f1c89f450ba30cd80d8543c4..41595bd8f0db9672dbd41de0b0df9d4309f40bf1 100644
--- a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
@@ -292,7 +292,7 @@ class KLocal implements Local {
 }
 
 /// TODO(johnniwinther,efortuna): Implement this.
-class KernelClosureClassMaps implements ClosureClassMaps {
+class KernelClosureClassMaps implements ClosureClassMaps<ir.Node> {
   const KernelClosureClassMaps();
 
   @override
@@ -304,6 +304,11 @@ class KernelClosureClassMaps implements ClosureClassMaps {
   ClosureClassMap getMemberMap(MemberEntity member) {
     return new ClosureClassMap(null, null, null, null);
   }
+
+  @override
+  ClosureAnalysisInfo getClosureAnalysisInfo(ir.Node node) {
+    return const ClosureAnalysisInfo();
+  }
 }
 
 class KernelSorter implements Sorter {