dart2dart Preproces placeholders instead of renaming them lazily,

lib/compiler/implementation/dart_backend/backend.dart

Index: lib/compiler/implementation/dart_backend/backend.dart
diff --git a/lib/compiler/implementation/dart_backend/backend.dart b/lib/compiler/implementation/dart_backend/backend.dart
index 74b2bc7a0bea2fcd42898d2ec36bbe717376d876..0dd811ce17d979ea948092899e1ac4721c196149 100644
--- a/lib/compiler/implementation/dart_backend/backend.dart
+++ b/lib/compiler/implementation/dart_backend/backend.dart
@@ -75,7 +75,7 @@ class DartBackend extends Backend {
     classes.forEach(collectElement);
 
     ConflictingRenamer renamer =
-        new ConflictingRenamer(compiler, collector.placeholders);
+        new ConflictingRenamer(compiler, collector);
     Emitter emitter = new Emitter(compiler, renamer);
     resolvedElements.forEach((element, treeElements) {
       if (!shouldOutput(element)) return;