RFC: Start refactoring to provide more than a single backend.

lib/compiler/implementation/native_emitter.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.
 
 class NativeEmitter {
 
   Compiler compiler;
   StringBuffer nativeBuffer;
 
   // Classes that participate in dynamic dispatch. These are the
@@ skipping 67 matching lines @@
     nativeBuffer.add(nativeCode);
     nativeBuffer.add(';\n');
 
     void defineInstanceMember(String name, String value) {
       nativeBuffer.add("$className.$name = $value;\n");
     }
 
     for (Element member in classElement.members) {
       if (member.isInstanceMember()) {
         bool needGettersAndSetters = true;
-        compiler.emitter.addInstanceMember(
+        compiler.backend.emitter.addInstanceMember(
             member, needGettersAndSetters, defineInstanceMember);
       }
     }
   }
 
   bool isNativeLiteral(String quotedName) {
     return quotedName[1] === '=';
   }
 
   bool isNativeGlobal(String quotedName) {
@@ skipping 26 matching lines @@
     bool hasUsedSelectors = false;
 
     void defineInstanceMember(String name, String value) {
       hasUsedSelectors = true;
       nativeBuffer.add("$dynamicName('$name').$nativeName = $value;\n");
     }
 
     for (Element member in classElement.members) {
       if (member.isInstanceMember()) {
         bool needGettersAndSetters = true;
-        compiler.emitter.addInstanceMember(
+        compiler.backend.emitter.addInstanceMember(
           member, needGettersAndSetters, defineInstanceMember);
       }
     }
 
-    compiler.emitter.generateTypeTests(classElement, (Element other) {
+    compiler.backend.emitter.generateTypeTests(classElement, (Element other) {
       assert(requiresNativeIsCheck(other));
       defineInstanceMember(compiler.namer.operatorIs(other),
                            "function() { return true; }");
     });
 
     if (hasUsedSelectors) classesWithDynamicDispatch.add(classElement);
   }
 
   List<ClassElement> getDirectSubclasses(ClassElement cls) {
     List<ClassElement> result = directSubtypes[cls];
@@ skipping 224 matching lines @@
     String toStringName = compiler.namer.instanceMethodName(
         null, const SourceString('toString'), 0);
     objectProperties.add("$defPropName(Object.prototype, '$toStringName', ");
     objectProperties.add(
         'function() { return $toStringHelperName(this); });\n');
 
     // Finally, emit the code in the main buffer.
     targetBuffer.add('(function() {\n$objectProperties$nativeBuffer\n})();\n');
   }
 }