Fix the merge of locals handler logic.

sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(revision 27097)
+++ sdk/lib/_internal/compiler/implementation/types/simple_types_inferrer.dart	(working copy)
@@ -93,10 +93,6 @@
   TypeMask nonNullExact(DartType type) => new TypeMask.nonNullExact(type);
   TypeMask nonNullEmpty() => new TypeMask.nonNullEmpty();
 
-  TypeMask nullable(TypeMask type) {
-    return type.nullable();
-  }
-
   TypeMask allocateContainer(TypeMask type,
                              Node node,
                              Element enclosing,
@@ -2306,10 +2302,6 @@
     T currentType =
         handleDynamicSend(node, currentSelector, iteratorType, null);
 
-    // We nullify the type in case there is no element in the
-    // iterable.
-    currentType = types.nullable(currentType);
-
     if (node.expression.isThis()) {
       // Any reasonable implementation of an iterator would expose
       // this, so we play it safe and assume it will.