Implementation of null-aware operators.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
index fbe0cb49138da90f4ba503b378d9f34a40ba8a3e..3df2efe67f2973e2216eaad4786c06b281d1bcfc 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
@@ -844,6 +844,12 @@ abstract class IrBuilderVisitor extends ast.Visitor<ir.Primitive>
   }
 
   @override
+  ir.Primitive visitIfNull(
+      ast.Send node, ast.Node left, ast.Node right, _) {
+    internalError(node, "If-null not yet implemented in cps_ir");
+  }
+
+  @override
   ir.Primitive visitLogicalAnd(
       ast.Send node, ast.Node left, ast.Node right, _) {
     return translateLogicalOperator(left, right, isLazyOr: false);