Split KernelToElementMap mixins to match interfaces

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

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index 59c97a7e9d5ea448123c696bb253aa94d4ae8b92..1351c9ab4aaa5bc42f7cff20ac5713f66f4ff7ba 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -18,6 +18,7 @@ import '../elements/resolution_types.dart';
 import '../elements/types.dart';
 import '../js_backend/js_backend.dart';
 import '../kernel/element_map.dart';
+import '../kernel/element_map_mixins.dart';
 import '../kernel/kernel.dart';
 import '../native/native.dart' as native;
 import '../resolution/tree_elements.dart';
@@ -34,8 +35,9 @@ import 'types.dart';
 /// A helper class that abstracts all accesses of the AST from Kernel nodes.
 ///
 /// The goal is to remove all need for the AST from the Kernel SSA builder.
-class KernelAstAdapter extends KernelToElementMapMixin
-    implements KernelToLocalsMap, KernelToElementMapForImpact {
+class KernelAstAdapter extends KernelToElementMapBaseMixin
+    with KernelToElementMapForBuildingMixin, KernelToElementMapForImpactMixin
+    implements KernelToLocalsMap {
   final Kernel kernel;
   final JavaScriptBackend _backend;
   final Map<ir.Node, ast.Node> _nodeToAst;