Make closedWorld a property of ClosedWorldRefiner.

pkg/compiler/lib/src/universe/world_builder.dart

Index: pkg/compiler/lib/src/universe/world_builder.dart
diff --git a/pkg/compiler/lib/src/universe/world_builder.dart b/pkg/compiler/lib/src/universe/world_builder.dart
index 05cae632087b4e55bb370f00436ae9f815d95e30..fc649b94df1213a2d4dd81e8fd2424afa24ddea9 100644
--- a/pkg/compiler/lib/src/universe/world_builder.dart
+++ b/pkg/compiler/lib/src/universe/world_builder.dart
@@ -1103,6 +1103,10 @@ class ResolutionWorldBuilderImpl implements ResolutionWorldBuilder {
 ///
 /// This adds additional access to liveness of selectors and elements.
 abstract class CodegenWorldBuilder implements WorldBuilder {
+  /// Opens this world builder using [closedWorld] as the known superset of
+  /// possible runtime entities.
+  void open(ClosedWorld closedWorld);
+
   void forEachInvokedName(
       f(String name, Map<Selector, SelectorConstraints> selectors));
 
@@ -1134,6 +1138,7 @@ abstract class CodegenWorldBuilder implements WorldBuilder {
 
 class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
   final Backend _backend;
+  ClosedWorld __world;

[Siggi Cherem (dart-lang), 2017/01/03 17:46:08]

I guess this is really really private ;-)

 
   /// The set of all directly instantiated classes, that is, classes with a
   /// generative constructor that has been called directly and not only through
@@ -1202,9 +1207,17 @@ class CodegenWorldBuilderImpl implements CodegenWorldBuilder {
 
   CodegenWorldBuilderImpl(this._backend, this.selectorConstraintsStrategy);
 
-  // TODO(johnniwinther): Remove this hack:
-  ClosedWorld get _world =>
-      _backend.compiler.resolverWorld.closedWorldForTesting;
+  void open(ClosedWorld closedWorld) {
+    assert(invariant(NO_LOCATION_SPANNABLE, __world == null,
+        message: "CodegenWorldBuilder has already been opened."));
+    __world = closedWorld;
+  }
+
+  ClosedWorld get _world {
+    assert(invariant(NO_LOCATION_SPANNABLE, __world != null,
+        message: "CodegenWorldBuilder has not been opened."));
+    return __world;
+  }
 
   Iterable<ClassElement> get processedClasses => _processedClasses.keys
       .where((cls) => _processedClasses[cls].isInstantiated);