Access BackendUsage through ClosedWorld

pkg/compiler/lib/src/inferrer/node_tracer.dart

Index: pkg/compiler/lib/src/inferrer/node_tracer.dart
diff --git a/pkg/compiler/lib/src/inferrer/node_tracer.dart b/pkg/compiler/lib/src/inferrer/node_tracer.dart
index 64f5c2bfab16d41da6b200b6d1a9cd24670e3159..b30ae28563a0d665c971f998951a522aa04b2492 100644
--- a/pkg/compiler/lib/src/inferrer/node_tracer.dart
+++ b/pkg/compiler/lib/src/inferrer/node_tracer.dart
@@ -450,8 +450,8 @@ abstract class TracerVisitor implements TypeInformationVisitor {
       bailout('Returned from a closure');
     }
     if (info.element.isField &&
-        !inferrer.compiler.backend
-            .canFieldBeUsedForGlobalOptimizations(info.element)) {
+        !inferrer.compiler.backend.canFieldBeUsedForGlobalOptimizations(
+            info.element, inferrer.closedWorld)) {
       bailout('Escape to code that has special backend treatment');
     }
     addNewEscapeInformation(info);
@@ -464,7 +464,7 @@ abstract class TracerVisitor implements TypeInformationVisitor {
     }
     if (!inferrer.compiler.backend
         .canFunctionParametersBeUsedForGlobalOptimizations(
-            element.functionDeclaration)) {
+            element.functionDeclaration, inferrer.closedWorld)) {
       bailout('Escape to code that has special backend treatment');
     }
     if (isParameterOfListAddingMethod(element) ||