Split backend implementation of EnqueuerListener

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart

Index: pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
index 16e454a4c0f996d5f45564687519df7dc18f29ec..7b77410057bc3e27cb3dde20a62f230236f9836b 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
@@ -1032,7 +1032,8 @@ class Emitter implements js_emitter.Emitter {
   jsAst.Expression generateLibraryDescriptor(
       LibraryElement library, Fragment fragment) {
     var uri = "";
-    if (!compiler.options.enableMinification || backend.mustPreserveUris) {
+    if (!compiler.options.enableMinification ||
+        backend.mirrorsData.mustPreserveUris) {
       uri = library.canonicalUri;
       if (uri.scheme == 'file' && compiler.options.outputUri != null) {
         uri =
@@ -1086,7 +1087,7 @@ class Emitter implements js_emitter.Emitter {
         .add(new jsAst.FunctionDeclaration(constructorName, constructorAst));
 
     String fieldNamesProperty = FIELD_NAMES_PROPERTY_NAME;
-    bool hasIsolateSupport = backend.hasIsolateSupport;
+    bool hasIsolateSupport = backend.backendUsage.isIsolateInUse;
     jsAst.Node fieldNamesArray;
     if (hasIsolateSupport) {
       fieldNamesArray =
@@ -1632,7 +1633,7 @@ class Emitter implements js_emitter.Emitter {
     });
     emitMainOutputUnit(program.mainFragment.outputUnit, mainOutput);
 
-    if (backend.requiresPreamble && !backend.htmlLibraryIsLoaded) {
+    if (backend.backendUsage.requiresPreamble && !backend.htmlLibraryIsLoaded) {
       reporter.reportHintMessage(NO_LOCATION_SPANNABLE, MessageKind.PREAMBLE);
     }
     // Return the total program size.