dart2js cps: Generate direct field accesses a build-time.

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 90bc77245a06f4cd30138aa6ff50da25dcf6faad..517c4fa68762f31b4310f86185c4dfaa12c2f14b 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
@@ -2187,6 +2187,10 @@ class GlobalProgramInformation {
   TypeMask getTypeMaskForForeign(NativeBehavior behavior) {
     return TypeMaskFactory.fromNativeBehavior(behavior, _compiler);
   }
+
+  FieldElement locateSingleField(Selector selector, TypeMask type) {
+    return _compiler.world.locateSingleField(selector, type);
+  }
 }
 
 /// IR builder specific to the JavaScript backend, coupled to the [JsIrBuilder].