Move remaining helpers to BackendHelpers

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

Index: pkg/compiler/lib/src/common/backend_api.dart
diff --git a/pkg/compiler/lib/src/common/backend_api.dart b/pkg/compiler/lib/src/common/backend_api.dart
index b2d02b3f7e77d380ab381a582df1a720c9459518..17e73b5cbc89bae344afc2b21df4570bc7e01a54 100644
--- a/pkg/compiler/lib/src/common/backend_api.dart
+++ b/pkg/compiler/lib/src/common/backend_api.dart
@@ -36,6 +36,8 @@ import '../io/code_output.dart' show
     CodeBuffer;
 import '../io/source_information.dart' show
     SourceInformationStrategy;
+import '../js_backend/backend_helpers.dart' as js_backend show
+    BackendHelpers;
 import '../js_backend/js_backend.dart' as js_backend show
     JavaScriptBackend;
 import '../library_loader.dart' show
@@ -286,8 +288,8 @@ abstract class Backend {
     // TODO(johnniwinther): Remove this when patching is only done by the
     // JavaScript backend.
     Uri canonicalUri = library.canonicalUri;
-    if (canonicalUri == js_backend.JavaScriptBackend.DART_JS_HELPER ||
-        canonicalUri == js_backend.JavaScriptBackend.DART_INTERCEPTORS) {
+    if (canonicalUri == js_backend.BackendHelpers.DART_JS_HELPER ||
+        canonicalUri == js_backend.BackendHelpers.DART_INTERCEPTORS) {
       return true;
     }
     return false;