Compute NativeBehavior for foreign functions.

tests/compiler/dart2js/kernel/impact_test.dart

Index: tests/compiler/dart2js/kernel/impact_test.dart
diff --git a/tests/compiler/dart2js/kernel/impact_test.dart b/tests/compiler/dart2js/kernel/impact_test.dart
index 8f4cc14eb592ab1f41b96cd2130892b0eb7026c8..f75ccfb6eb1de8ab1a22f484aefd135448f600aa 100644
--- a/tests/compiler/dart2js/kernel/impact_test.dart
+++ b/tests/compiler/dart2js/kernel/impact_test.dart
@@ -602,7 +602,9 @@ main(List<String> args) {
         ]);
     compiler.resolution.retainCachesForTesting = true;
     await compiler.run(entryPoint);
-    checkLibrary(compiler, compiler.mainApp);
+    compiler.libraryLoader.libraries.forEach((LibraryElement library) {
+      checkLibrary(compiler, library);
+    });
   });
 }
 
@@ -622,6 +624,18 @@ void checkLibrary(Compiler compiler, LibraryElement library) {
 }
 
 void checkElement(Compiler compiler, AstElement element) {
+  if (compiler.backend.isNative(element)) {
+    // Skip native functions for now; kernel does not provide their
+    // signature which we need to derive their native behavior.
+    return;
+  }
+  if (element.isConstructor) {
+    ConstructorElement constructor = element;
+    if (constructor.isRedirectingFactory) {
+      // Skip redirecting constructors for now; they might not be supported.
+      return;
+    }
+  }
   ResolutionImpact astImpact = compiler.resolution.getResolutionImpact(element);
   astImpact = laxImpact(compiler, element, astImpact);
   ResolutionImpact kernelImpact = build(compiler, element.resolvedAst);