Compute and cache element NativeBehavior during resolution.

pkg/compiler/lib/src/common/backend_api.dart

Index: pkg/compiler/lib/src/common/backend_api.dart
diff --git a/pkg/compiler/lib/src/common/backend_api.dart b/pkg/compiler/lib/src/common/backend_api.dart
index 080a03b416a96f7d048d823bbefb37682f8da139..5bbb2f0655fc8a834b644ec6d30716ef4bed56be 100644
--- a/pkg/compiler/lib/src/common/backend_api.dart
+++ b/pkg/compiler/lib/src/common/backend_api.dart
@@ -44,7 +44,7 @@ import 'registry.dart' show Registry;
 import 'tasks.dart' show CompilerTask;
 import 'work.dart' show ItemCompilationContext;
 
-abstract class Backend implements Target {
+abstract class Backend extends Target {
   final Compiler compiler;
 
   Backend(this.compiler);
@@ -404,6 +404,12 @@ abstract class Backend implements Target {
   EnqueueTask makeEnqueuer() => new EnqueueTask(compiler);
 }
 
+/// Interface for resolving native data for a target specific element.
+abstract class NativeRegistry {
+  /// Registers [nativeData] as part of the resolution impact.
+  void registerNativeData(dynamic nativeData);
+}
+
 /// Interface for resolving calls to foreign functions.
 abstract class ForeignResolver {
   /// Returns the constant expression of [node], or `null` if [node] is not