Revert r27592, some unit tests fail.

sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart	(revision 27592)
+++ sdk/lib/_internal/compiler/implementation/dart_backend/placeholder_collector.dart	(working copy)
@@ -44,10 +44,10 @@
 class SendVisitor extends ResolvedVisitor {
   final PlaceholderCollector collector;
 
-  SendVisitor(collector, TreeElements elements)
-      : this.collector = collector,
-        super(elements, collector.compiler);
+  get compiler => collector.compiler;
 
+  SendVisitor(this.collector, TreeElements elements) : super(elements);
+
   visitOperatorSend(Send node) {
   }
 
@@ -104,10 +104,6 @@
     }
   }
 
-  visitAssert(node) {
-    visitStaticSend(node);
-  }
-
   visitStaticSend(Send node) {
     final element = elements[node];
     collector.backend.registerStaticSend(element, node);