Move towards using WorldImpact for codegen

pkg/compiler/lib/src/js_backend/type_variable_handler.dart

Index: pkg/compiler/lib/src/js_backend/type_variable_handler.dart
diff --git a/pkg/compiler/lib/src/js_backend/type_variable_handler.dart b/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
index ada9d167a6e5f0843640de687723b982450f9086..d7c3281f056ff48349ad0bc3dfd0a8d450816848 100644
--- a/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
+++ b/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
@@ -15,6 +15,7 @@ import '../js_emitter/js_emitter.dart'
     show CodeEmitterTask, MetadataCollector, Placeholder;
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/use.dart' show StaticUse;
+import '../universe/world_impact.dart';
 import '../util/util.dart';
 import 'backend.dart';
 
@@ -44,6 +45,10 @@ class TypeVariableHandler {
   Map<TypeVariableElement, jsAst.Expression> _typeVariableConstants =
       new Map<TypeVariableElement, jsAst.Expression>();
 
+  /// Impact builder used for the codegen world computation.
+  // TODO(johnniwinther): Add impact builder for resolution.
+  final StagedWorldImpactBuilder impactBuilder = new StagedWorldImpactBuilder();
+
   TypeVariableHandler(this._compiler);
 
   ClassElement get _typeVariableClass => _backend.helpers.typeVariableClass;
@@ -52,6 +57,12 @@ class TypeVariableHandler {
   JavaScriptBackend get _backend => _compiler.backend;
   DiagnosticReporter get reporter => _compiler.reporter;
 
+  void onQueueEmpty(Enqueuer enqueuer) {
+    if (enqueuer.isResolutionQueue) return;
+
+    enqueuer.applyImpact(null, impactBuilder.flush());
+  }
+
   void registerClassWithTypeVariables(
       ClassElement cls, Enqueuer enqueuer, Registry registry) {
     if (enqueuer.isResolutionQueue) {
@@ -108,9 +119,8 @@ class TypeVariableHandler {
 
       _backend.constants.evaluate(constant);
       ConstantValue value = _backend.constants.getConstantValue(constant);
-      _backend.registerCompileTimeConstant(value, _compiler.globalDependencies);
+      _backend.computeImpactForCompileTimeConstant(value, impactBuilder, false);
       _backend.addCompileTimeConstantForEmission(value);
-      _backend.constants.addCompileTimeConstantForEmission(value);
       constants
           .add(_reifyTypeVariableConstant(value, currentTypeVariable.element));
     }