Decouple WorkItem from Compiler

pkg/compiler/lib/src/common/codegen.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.common.codegen;
 
 import '../common.dart';
-import '../compiler.dart' show Compiler;
+import '../common/backend_api.dart' show Backend;
 import '../constants/values.dart' show ConstantValue;
 import '../dart_types.dart' show DartType, InterfaceType;
 import '../elements/elements.dart'
     show
         AstElement,
         ClassElement,
         Element,
         FunctionElement,
         LocalFunctionElement,
         ResolvedAst;
@@ skipping 120 matching lines @@
   }
 
   Iterable<Element> get asyncMarkers {
     return _asyncMarkers != null ? _asyncMarkers : const <FunctionElement>[];
   }
 }
 
 // TODO(johnniwinther): Split this class into interface and implementation.
 // TODO(johnniwinther): Move this implementation to the JS backend.
 class CodegenRegistry {
-  final Compiler compiler;
   final Element currentElement;
   final _CodegenImpact worldImpact;
 
-  CodegenRegistry(Compiler compiler, AstElement currentElement)
-      : this.compiler = compiler,
-        this.currentElement = currentElement,
+  CodegenRegistry(AstElement currentElement)
+      : this.currentElement = currentElement,
         this.worldImpact = new _CodegenImpact();
 
   bool get isForResolution => false;
 
   String toString() => 'CodegenRegistry for $currentElement';
 
   /// Add the uses in [impact] to the impact of this registry.
   void addImpact(WorldImpact impact) {
     worldImpact.addImpact(impact);
   }
@@ skipping 50 matching lines @@
 
   void registerAsyncMarker(FunctionElement element) {
     worldImpact.registerAsyncMarker(element);
   }
 }
 
 /// [WorkItem] used exclusively by the [CodegenEnqueuer].
 class CodegenWorkItem extends WorkItem {
   CodegenRegistry registry;
   final ResolvedAst resolvedAst;
+  final Backend backend;
 
-  factory CodegenWorkItem(Compiler compiler, AstElement element) {
+  factory CodegenWorkItem(Backend backend, AstElement element) {
     // If this assertion fails, the resolution callbacks of the backend may be
     // missing call of form registry.registerXXX. Alternatively, the code
     // generation could spuriously be adding dependencies on things we know we
     // don't need.
     assert(invariant(element, element.hasResolvedAst,
         message: "$element has no resolved ast."));
     ResolvedAst resolvedAst = element.resolvedAst;
-    return new CodegenWorkItem.internal(resolvedAst);
+    return new CodegenWorkItem.internal(resolvedAst, backend);
   }
 
-  CodegenWorkItem.internal(ResolvedAst resolvedAst)
+  CodegenWorkItem.internal(ResolvedAst resolvedAst, this.backend)
       : this.resolvedAst = resolvedAst,
         super(resolvedAst.element);
 
-  WorldImpact run(Compiler compiler, Enqueuer world) {
-    if (world.isProcessed(element)) return const WorldImpact();
-
-    registry = new CodegenRegistry(compiler, element);
-    return compiler.codegen(this, world);
+  WorldImpact run() {
+    registry = new CodegenRegistry(element);
+    return backend.codegen(this);
   }
 
   String toString() => 'CodegenWorkItem(${resolvedAst.element})';
 }