dart2js: Move most of the code_emitter_task code into the program-builder.

pkg/compiler/lib/src/js_emitter/native_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/native_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/native_emitter.dart b/pkg/compiler/lib/src/js_emitter/native_emitter.dart
index 56bb8de4c14d5b3ecc7d1313fb40797560913be7..4487f8fc3a26dd22dbffabc04ccdfd0e5cb93285 100644
--- a/pkg/compiler/lib/src/js_emitter/native_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/native_emitter.dart
@@ -61,8 +61,16 @@ class NativeEmitter {
    *
    * [classes] contains native classes, mixin applications, and user subclasses
    * of native classes.
+   *
+   * [interceptorClassesNeededByConstants] contains the interceptors that are
+   * referenced by constants.
+   *
+   * [classesModifiedByEmitRTISupport] contains the list of classes that must
+   * exist, because runtime-type support adds information to the class.
    */
-  Set<Class> prepareNativeClasses(List<Class> classes) {
+  Set<Class> prepareNativeClasses(List<Class> classes,
+      Set<ClassElement> interceptorClassesNeededByConstants,
+      Set<ClassElement> classesModifiedByEmitRTISupport) {
     assert(classes.every((Class cls) => cls != null));
 
     hasNativeClasses = classes.isNotEmpty;
@@ -103,11 +111,6 @@ class NativeEmitter {
 
     neededClasses.add(objectClass);
 
-    Set<ClassElement> neededByConstant = emitterTask
-        .computeInterceptorsReferencedFromConstants();
-    Set<ClassElement> modifiedClasses = emitterTask.typeTestRegistry
-        .computeClassesModifiedByEmitRuntimeTypeSupport();
-
     for (Class cls in preOrder.reversed) {
       ClassElement classElement = cls.element;
       // Post-order traversal ensures we visit the subclasses before their
@@ -121,9 +124,9 @@ class NativeEmitter {
         needed = true;
       } else if (!isTrivialClass(cls)) {
         needed = true;
-      } else if (neededByConstant.contains(classElement)) {
+      } else if (interceptorClassesNeededByConstants.contains(classElement)) {
         needed = true;
-      } else if (modifiedClasses.contains(classElement)) {
+      } else if (classesModifiedByEmitRTISupport.contains(classElement)) {
         // TODO(9556): Remove this test when [emitRuntimeTypeSupport] no longer
         // adds information to a class prototype or constructor.
         needed = true;